Stumped with Lights Issue
March 15th, 2021, 1:11 PM
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Stumped with Lights Issue
Hi all, been researching for a week now and still stumped.
Problem: the lights on my 2004 Chevy Express 5.3 AWD stay on for about 10 min after I shut the engine off. It seems to be that power is getting to the "full on" light circuit and it is connected to something that turns that power off after about 10 min.
My guess is that there is a short in a wire or a Body Control Module is going bad or both. But if I can know where the residual power is coming from it would be greatly helpful in tracing down the issue.
Below are the symptoms and what I have tried so far.
The Symptoms:
Background, about 3 months ago we had a bad alternator that let the battery die while we were driving. New battery, new alternator.
1. Two weeks ago, the DRL started coming on/off randomly. If I turned the light switch to Headlights On while driving, it would stop. Everything else normal.
2. Then 4 days ago, it progressed to all the exterior lights (Headlights/Tail Lights/ Marker Lights) and the dash lights would stay on even when the switch is off. I could resolve by lightly bumping the dash near the light switch and softly closing the door.
3. Now the exterior lights and dash lights stay on for 10min after I turn off the van, though I can make the lights blink off by pounding on the dash, and sometimes I can get the "lights on" chime to stop by pounding on the dash when the door is open.
What I tried:
1. With key removed and door open, I disconnected the light switch; the exterior lights and dash lights remained on and the interior dome lights (switched off) came on. I could still influence the lights to blink off by pounding on the dash.
2. I removed the DLR Module (replaced 3 yrs ago) and the DLR fuses; same result as #1.
3. I switched the hight/low headlight relays; no change.
4. I checked the delayed power on the radio, windows and dome lights; works as normal.
Problem: the lights on my 2004 Chevy Express 5.3 AWD stay on for about 10 min after I shut the engine off. It seems to be that power is getting to the "full on" light circuit and it is connected to something that turns that power off after about 10 min.
My guess is that there is a short in a wire or a Body Control Module is going bad or both. But if I can know where the residual power is coming from it would be greatly helpful in tracing down the issue.
Below are the symptoms and what I have tried so far.
The Symptoms:
Background, about 3 months ago we had a bad alternator that let the battery die while we were driving. New battery, new alternator.
1. Two weeks ago, the DRL started coming on/off randomly. If I turned the light switch to Headlights On while driving, it would stop. Everything else normal.
2. Then 4 days ago, it progressed to all the exterior lights (Headlights/Tail Lights/ Marker Lights) and the dash lights would stay on even when the switch is off. I could resolve by lightly bumping the dash near the light switch and softly closing the door.
3. Now the exterior lights and dash lights stay on for 10min after I turn off the van, though I can make the lights blink off by pounding on the dash, and sometimes I can get the "lights on" chime to stop by pounding on the dash when the door is open.
What I tried:
1. With key removed and door open, I disconnected the light switch; the exterior lights and dash lights remained on and the interior dome lights (switched off) came on. I could still influence the lights to blink off by pounding on the dash.
2. I removed the DLR Module (replaced 3 yrs ago) and the DLR fuses; same result as #1.
3. I switched the hight/low headlight relays; no change.
4. I checked the delayed power on the radio, windows and dome lights; works as normal.
March 15th, 2021, 8:34 PM
#2
CF Junior Member
Since we're talking about DRL, chime and dashlight here... I suspect them to be activated by the ignition switch when a vehicle is equiped with DRL ? I mean you have no choice to turn these on or off because it is automatic as soon as you turn the key to ignition position.
Then it could be a good thing to check for a faulty ignition switch. Check for voltage at the pink and yellow wire when the key is removed. This is where your residual power might come from. What makes me think it is not the BCM is when you say pounding on the dash turn them off.
It could be that even when the ignition key is at OFF or even completely removed... the switch is still sending a signal to the BCM to turn the DRL ON.
Good luck
Then it could be a good thing to check for a faulty ignition switch. Check for voltage at the pink and yellow wire when the key is removed. This is where your residual power might come from. What makes me think it is not the BCM is when you say pounding on the dash turn them off.
It could be that even when the ignition key is at OFF or even completely removed... the switch is still sending a signal to the BCM to turn the DRL ON.
Good luck
Last edited by pomerlo; March 15th, 2021 at 9:06 PM.
March 15th, 2021, 9:04 PM
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Thank you for your thoughtful reply Pomerlo!
I will certainly add that in as something to look at. Glad to hear it doesn’t sound like a bcm. You do have a valid point as the problem seems to restart every time I turn the ignition to on.
I will add that the DRL with my US model only turns on marker lights on the front when my light switch is set to off and I go into drive gear. My current situation is “full lights on” like when the light switch is set to headlights on (headlights, tail lights, dash lights in addition to the marker lights). So actually my DRL is not on at all since the normal lights are on.
it seems more like something is powering the headlight circuit but only for 10 mins of delayed power, and in a way that ignores the door switch that cancels the residual power to the radio and windows.
I will certainly add that in as something to look at. Glad to hear it doesn’t sound like a bcm. You do have a valid point as the problem seems to restart every time I turn the ignition to on.
I will add that the DRL with my US model only turns on marker lights on the front when my light switch is set to off and I go into drive gear. My current situation is “full lights on” like when the light switch is set to headlights on (headlights, tail lights, dash lights in addition to the marker lights). So actually my DRL is not on at all since the normal lights are on.
it seems more like something is powering the headlight circuit but only for 10 mins of delayed power, and in a way that ignores the door switch that cancels the residual power to the radio and windows.
March 15th, 2021, 9:34 PM
#4
CF Junior Member
Ok got ya... Then another place to check could be the headlight switch .... according to the Lighting system description below.
Taken from the service manual.... It might help you to find a place to start.
Let me know if you need a particular wiring diagram.2004 Chevrolet Express | Express, Savana (VIN G/H) Service Manual | Body | Wiring Systems | Component Locator | Document ID: 885612
Exterior Lighting Systems Description and Operation
Exterior Lamps
The exterior lighting system consist of the following lamps:
•
The headlamps
•
The daytime running lamps (DRL)
•
The park, tail and marker lamps
•
The turn signal/hazard lamps
•
The stop lamps
•
The backup lamps
Headlamps
Headlamp ON/OFF control is determined by the body control module (BCM) by a signal on the headlamp switch on input circuit when the headlamp switch is in the HEAD position.
If the headlight switch is left in the ON position, the inadvertent power control feature will turn off the headlights approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the headlights will remain on until turned off or the battery runs dead.
The high beam indicator is illuminated when the instrument cluster receives a class 2 serial data message from the BCM that the high beams are illuminated.
High Beams
The high beam headlamps receive voltage from the HDLP-HIBM relay located in the underhood fuse block. The BCM controls the relay on the headlamp high beam relay control circuit. High beam control is determined by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp dimmer switch signal circuit is grounded, the BCM grounds the headlamp high beam relay control circuit, illuminating the high beam headlamps. The right and left high beam circuits are independent and are fused independently in the underhood fuse block. The right and left headlamps are grounded at G100 and G101.
Low Beams
The low beam headlamps receive voltage from the HDLP-LOBM relay located in the underhood fuse block. The BCM controls the relay on the headlamp low beam relay control circuit. Low beam control is determined by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp dimmer switch signal circuit is open, the BCM grounds the headlamp low beam relay control circuit, illuminating the low beam headlamps. The right and left low beam circuits are independent and are fused independently in the underhood fuse block. The right and left headlamps are grounded at G100 and G101.
Daytime Running Lamps (DRL)
The DRL are a function of the front turn signal lamps. The DRL will operate when the ignition switch is in the RUN position, the gear selector is not in the PARK position, and the headlamp switch is in the OFF position. When the BCM receives these signals it will signal the turn/hazard flasher module to turn on the DRL by grounding the DRL low control signal. The turn/hazard flasher module supplies voltage to the DRL on the right and left DRL/turn supply voltage circuits. If a front turn signal lamp is inoperative the DRL will not operate.
The DRL can be deactivated by turning the headlamp switch to the DRL OFF position while the DRL are operating. The DRL defeat position of the headlamp switch is a momentary ground signal to the BCM to command the DRL function ON or OFF. After each key cycle the BCM will default to the DRL ON function.
Park, Tail and Marker Lamps
The park, tail and marker lamps, including the license lamps, are turned on when the headlamp switch is placed in the PARK or HEAD position. The headlamp and panel dimmer switch supplies a ground signal to the BCM on the park lamps switch on signal circuit. The underhood fuse block supplies battery positive voltage to both the park lamp relay switch contacts and the park lamp coil circuit. The body control module (BCM) provides a ground or control circuit to the park lamp relay coil circuit. When the park lamps are turned on the BCM energizes the park lamp relay. Current flow is from the park lamp relay to these fuses in the body fuse block:
•
FR PARK
•
LR PARK
•
RR PARK
•
TRLR PARK
•
UPFTR PRK
The front park and marker lamps are grounded at G100 and G101. The rear park and license lamps are grounded at G401 and 402.
Turn Signal/Hazard Lamps
The IGN E 10 A fuse in the underhood fuse block supplies battery positive voltage to the turn signal switch assembly. Ground for the hazard switch is from G302. The FLASHER 15 A fuse in the underhood fuse block supplies battery positive voltage to the turn/hazard flasher module. When the turn signal switch is placed in either the left or right position, a voltage signal is completed from the turn signal switch to the turn/hazard flasher module. When the hazard flasher switch is activated, a ground signal is completed from the hazard switch to the turn/hazard flasher module. The turn/hazard flasher module then sends an on-off voltage signal to the appropriate turn signal lamps, or to all turn signal lamps for hazard operation through these fuses:
•
DR TRN MIR, in the body fuse block
•
PASS TRN MIR, in the body fuse block
•
LR STOP/TRN, in the body fuse block, and in the underhood fuse block for RPO UY7
•
RR STOP/TRN, in the body fuse block, and in the underhood fuse block for RPO UY7
•
LR TURN in the underhood fuse block
•
RR TURN in the underhood fuse block
•
LT DRL/TRN in the underhood fuse block
•
RT DRL/TRN in the underhood fuse block
The audio chime is also activated when the turn signals are on. When the hazard switch is pressed, all turn signal lamps will flash including both IPC turn indicators. The front turn signals are grounded at G100 and G101. The rear turn signals are grounded at G401 and 402. The mirror turn signals are grounded through a splice pack at G347.
Stop Lamps
The STOP LP 15 A fuse in the underhood fuse block supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to the STOP/CHMSL fuse and through the turn/hazard flasher module to the LR STOP/TRN and RR STOP/TRN fuses in the body fuse block or the LR TURN and RR TURN fuses in the underhood fuse block. The voltage from the STOP/CHMSL fuse is to the CHMSL and cruise control. The voltage from the LR STOP/TRN and RR STOP/TRN fuses is to the rear stop lamps. The voltage from the LR TURN and RR TURN fuses is to the trailer stop/turn relays. The rear stop lamps are grounded at G401 and 402. The CHMSL is grounded at G401
Backup Lamps
The B/U LP 20 A fuse in the underhood fuse block supplies battery positive voltage to the normally open park neutral position (PNP) switch. When driver places the gear selector lever is in the REVERSE position, the switch closes and the voltage is from the switch to the powertrain control module (PCM). The PCM signals the BCM on the class II serial data circuits that the backup lamps are requested. The BCM supplies voltage on the backup lamp supply voltage circuit to the backup lamps and to the automatic day/night mirror. The backup lamps are grounded at G401. Voltage for the backup lamp supply voltage, without RPO YF7 the courtesy lamp supply voltage, and with RPO YF7 the courtesy lamp high control circuits is from the TBC 2 fuse 18 in the underhood fuse block directly through the BCM to these circuits.
© 2021 General Motors Corporation. All rights reserved.
Taken from the service manual.... It might help you to find a place to start.
Let me know if you need a particular wiring diagram.2004 Chevrolet Express | Express, Savana (VIN G/H) Service Manual | Body | Wiring Systems | Component Locator | Document ID: 885612
Exterior Lighting Systems Description and Operation
Exterior Lamps
The exterior lighting system consist of the following lamps:
•
The headlamps
•
The daytime running lamps (DRL)
•
The park, tail and marker lamps
•
The turn signal/hazard lamps
•
The stop lamps
•
The backup lamps
Headlamps
Headlamp ON/OFF control is determined by the body control module (BCM) by a signal on the headlamp switch on input circuit when the headlamp switch is in the HEAD position.
If the headlight switch is left in the ON position, the inadvertent power control feature will turn off the headlights approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the headlights will remain on until turned off or the battery runs dead.
The high beam indicator is illuminated when the instrument cluster receives a class 2 serial data message from the BCM that the high beams are illuminated.
High Beams
The high beam headlamps receive voltage from the HDLP-HIBM relay located in the underhood fuse block. The BCM controls the relay on the headlamp high beam relay control circuit. High beam control is determined by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp dimmer switch signal circuit is grounded, the BCM grounds the headlamp high beam relay control circuit, illuminating the high beam headlamps. The right and left high beam circuits are independent and are fused independently in the underhood fuse block. The right and left headlamps are grounded at G100 and G101.
Low Beams
The low beam headlamps receive voltage from the HDLP-LOBM relay located in the underhood fuse block. The BCM controls the relay on the headlamp low beam relay control circuit. Low beam control is determined by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamp dimmer switch signal circuit is open, the BCM grounds the headlamp low beam relay control circuit, illuminating the low beam headlamps. The right and left low beam circuits are independent and are fused independently in the underhood fuse block. The right and left headlamps are grounded at G100 and G101.
Daytime Running Lamps (DRL)
The DRL are a function of the front turn signal lamps. The DRL will operate when the ignition switch is in the RUN position, the gear selector is not in the PARK position, and the headlamp switch is in the OFF position. When the BCM receives these signals it will signal the turn/hazard flasher module to turn on the DRL by grounding the DRL low control signal. The turn/hazard flasher module supplies voltage to the DRL on the right and left DRL/turn supply voltage circuits. If a front turn signal lamp is inoperative the DRL will not operate.
The DRL can be deactivated by turning the headlamp switch to the DRL OFF position while the DRL are operating. The DRL defeat position of the headlamp switch is a momentary ground signal to the BCM to command the DRL function ON or OFF. After each key cycle the BCM will default to the DRL ON function.
Park, Tail and Marker Lamps
The park, tail and marker lamps, including the license lamps, are turned on when the headlamp switch is placed in the PARK or HEAD position. The headlamp and panel dimmer switch supplies a ground signal to the BCM on the park lamps switch on signal circuit. The underhood fuse block supplies battery positive voltage to both the park lamp relay switch contacts and the park lamp coil circuit. The body control module (BCM) provides a ground or control circuit to the park lamp relay coil circuit. When the park lamps are turned on the BCM energizes the park lamp relay. Current flow is from the park lamp relay to these fuses in the body fuse block:
•
FR PARK
•
LR PARK
•
RR PARK
•
TRLR PARK
•
UPFTR PRK
The front park and marker lamps are grounded at G100 and G101. The rear park and license lamps are grounded at G401 and 402.
Turn Signal/Hazard Lamps
The IGN E 10 A fuse in the underhood fuse block supplies battery positive voltage to the turn signal switch assembly. Ground for the hazard switch is from G302. The FLASHER 15 A fuse in the underhood fuse block supplies battery positive voltage to the turn/hazard flasher module. When the turn signal switch is placed in either the left or right position, a voltage signal is completed from the turn signal switch to the turn/hazard flasher module. When the hazard flasher switch is activated, a ground signal is completed from the hazard switch to the turn/hazard flasher module. The turn/hazard flasher module then sends an on-off voltage signal to the appropriate turn signal lamps, or to all turn signal lamps for hazard operation through these fuses:
•
DR TRN MIR, in the body fuse block
•
PASS TRN MIR, in the body fuse block
•
LR STOP/TRN, in the body fuse block, and in the underhood fuse block for RPO UY7
•
RR STOP/TRN, in the body fuse block, and in the underhood fuse block for RPO UY7
•
LR TURN in the underhood fuse block
•
RR TURN in the underhood fuse block
•
LT DRL/TRN in the underhood fuse block
•
RT DRL/TRN in the underhood fuse block
The audio chime is also activated when the turn signals are on. When the hazard switch is pressed, all turn signal lamps will flash including both IPC turn indicators. The front turn signals are grounded at G100 and G101. The rear turn signals are grounded at G401 and 402. The mirror turn signals are grounded through a splice pack at G347.
Stop Lamps
The STOP LP 15 A fuse in the underhood fuse block supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to the STOP/CHMSL fuse and through the turn/hazard flasher module to the LR STOP/TRN and RR STOP/TRN fuses in the body fuse block or the LR TURN and RR TURN fuses in the underhood fuse block. The voltage from the STOP/CHMSL fuse is to the CHMSL and cruise control. The voltage from the LR STOP/TRN and RR STOP/TRN fuses is to the rear stop lamps. The voltage from the LR TURN and RR TURN fuses is to the trailer stop/turn relays. The rear stop lamps are grounded at G401 and 402. The CHMSL is grounded at G401
Backup Lamps
The B/U LP 20 A fuse in the underhood fuse block supplies battery positive voltage to the normally open park neutral position (PNP) switch. When driver places the gear selector lever is in the REVERSE position, the switch closes and the voltage is from the switch to the powertrain control module (PCM). The PCM signals the BCM on the class II serial data circuits that the backup lamps are requested. The BCM supplies voltage on the backup lamp supply voltage circuit to the backup lamps and to the automatic day/night mirror. The backup lamps are grounded at G401. Voltage for the backup lamp supply voltage, without RPO YF7 the courtesy lamp supply voltage, and with RPO YF7 the courtesy lamp high control circuits is from the TBC 2 fuse 18 in the underhood fuse block directly through the BCM to these circuits.
© 2021 General Motors Corporation. All rights reserved.
Last edited by pomerlo; March 15th, 2021 at 10:02 PM.
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MitchM (March 30th, 2023)
March 15th, 2021, 9:52 PM
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Yes, it does look like the headlight switch is involved, like if the switch is internally stuck on and has lost the ability to turn off, then this description of the BCM turning off the lights that were left on after 10 min describes the behavior quite well.
I think the fact that I could still influence the situation by banging with the switch unplugged threw me off from blaming the switch. It could be a compound problem, but the switch is a good place to start. I will keep you posted!
thank you.
I think the fact that I could still influence the situation by banging with the switch unplugged threw me off from blaming the switch. It could be a compound problem, but the switch is a good place to start. I will keep you posted!
thank you.
March 15th, 2021, 10:11 PM
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March 19th, 2021, 5:25 AM
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Ok, I replaced the light switch and now have control of turning on and off the lights again. When I opened the old switch it was clear that the contacts for the headlights had made a grove in the circuit bird side and had simply worn itself out. Thanks for your help on that!
As I expected, the issue is a compound one. I’m still getting an infrequent flickering of the DRL light on my dash when I go down bumpy roads. I expect this corresponds to why I can influence the lights when I pound on the dash even with the switch unplugged.
Wondering where to go from here. Assuming the switch is good now, the DRL/blinker module could be bad again (3yrs old) or there could be a short in the wiring. Thoughts?
As I expected, the issue is a compound one. I’m still getting an infrequent flickering of the DRL light on my dash when I go down bumpy roads. I expect this corresponds to why I can influence the lights when I pound on the dash even with the switch unplugged.
Wondering where to go from here. Assuming the switch is good now, the DRL/blinker module could be bad again (3yrs old) or there could be a short in the wiring. Thoughts?
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March 19th, 2021, 7:58 AM
#8
CF Junior Member
Can you give more details of whats hapening ? Is the light switch to off position when the lights flicker ? what ahppen when you pound the dash with the switch ON ? What is the state of the lights when you pound on the dash ? Are they turning off completely until you bang again ? Is there a part of the dash that is more responsive thant the other ?
Last edited by pomerlo; March 19th, 2021 at 8:03 AM.
March 19th, 2021, 8:04 AM
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Yes, when the light switch is off and the vehicle is in drive the DRL light comes on (normal) but occasionally when hitting some bumps the DRL light flickers off. I can hear the relays in the module clicking which draws my attention to it. Is there a way to test if the issue is in the module or in the wiring?
I know some who simply pull the DRL fuses and call it a day as that is not a legal requirement in my state, but I think it is either a simple module replacement or a symptom of a deeper problem like a ground or shorting issue.
I know some who simply pull the DRL fuses and call it a day as that is not a legal requirement in my state, but I think it is either a simple module replacement or a symptom of a deeper problem like a ground or shorting issue.
March 19th, 2021, 1:15 PM
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Ok, so The remaining symptoms may be temperature dependent.
Today it was in the 30’s and twice before I turned on the van the full lights on of the van came on when I shut a door. Then going down the road, the DRL flickered on and off a bit with bumps. However, after the van interior was warmed up, the symptoms went away.
I’m leaning toward the DRL module has gone bad again, since the last time it was bad it was highly temperature dependent.
however, I don’t think the DRL has anything to do with the headlights. Open to thoughts here. Hopefully this thread will help someone else as I couldn’t find anything specifically on this.
Today it was in the 30’s and twice before I turned on the van the full lights on of the van came on when I shut a door. Then going down the road, the DRL flickered on and off a bit with bumps. However, after the van interior was warmed up, the symptoms went away.
I’m leaning toward the DRL module has gone bad again, since the last time it was bad it was highly temperature dependent.
however, I don’t think the DRL has anything to do with the headlights. Open to thoughts here. Hopefully this thread will help someone else as I couldn’t find anything specifically on this.