hlg1111

I have a 2002 Chevy Tracker, 6 cyl. I just had it inspected 2 weeks ago. I started it up yesterday and Service Soon Light came on. It ran ok, took it home hooked it up to scanner.. p0155 p0135 p0161 p0141, O2 heater codes came up all at the same time. Meaning all four O2 sensors had the same heater fault code.. I never heard of this before. Cleared the codes, started the engine, code light came on instantly. Has anyone else had this problem? Is there a wiring diagram somewhere online for 2002 Chevy Tracker?

Henry

L84sky

Inspect fuse and report back.



The H02S fuse (and H02S relay) feed all four 02 heater circuits.



The fuse is located inside this box on the junction block near your left foot.



It's a regular (full size) 15 amp fuse.

Irish_alley

hey L8 where you getting the trouble shooting pictures?

L84sky

Factory Service Manual

hlg1111

Thank You L84sky. So I found the fuse location from the pictures you provided. It was blown.. I had a bad feeling about this.. So I replaced it and started the engine. Drove around a block back to my home. Checked the fuse and it's blown again. I guess I'll have to go under the car and see if there are any shorts that I can see with my eyes. Any other suggestions?

Henry

L84sky

Continue trouble shooting from step 14. The problem is most likely a shorted heater in one of the four O2 sensors but you have to rule out a wiring problem first.





All four O2 sensor heaters share the HO2S fuse so any one of them could be causing the fuse to blow.



The HO2S relay is under the hood near the wiper fluid bottle. I would disconnect the negative lead from the battery.
Get an ohmmeter, pull the relay, use the schematics to probe pins 1 and 2 of the relay socket for a short to the frame.
No short on pin 1 means the wiring is good from the fuse to the relay. No short on pin 2 means wiring to the O2
heaters and onto the PCM is probably good. But a shorted O2 heater will not show up on this test because the
internal PCM switches that supply a ground will be open when the key is OFF. If possible, unplug all four O2
sensor connectors. If the fuse does not blow now the problem is one of the heaters. Reconnect them one at a
time to find the culprit.



I don't have the pinout for the O2 relay but it's similar to this one for the horn relay. Pin one
goes back to the fuse. Pin two goes the O2 sensors.

hlg1111

Thank You again, L84sky. I will try this over the weekend. I'll let you know how it turned out..

Henry

L84sky

I'll keep my fingers crossed for you.

hlg1111

Hello L84sky

I finally did what you told me to do a year ago, to try to find the short. I took off both the Positive and Negative battery terminals, put the ohm meter on "Beep" for continuity, grounded the probe on side of engine and put the other probe into 1 and then 2, and I didn't get a "beep". I tried probe on 4 got a "beep". If I read the schematic right 4 should be ground, so you would expect that. Tried in 3 and got a "beep", not what I expected. I did this with a new fuse in, ignition off. Could it be the relay?

So I know it's been over a year since I first posted this in this forum, but when I first posted this, I just got my car inspected, so I had a year to work on it. but I'm a procrastinator. lol My inspection was due at the end of April, but since this Covid thing, I have till the end of May.

Henry

L84sky

Continuity to ground on pin 4 is normal. Ground on pin 3 is not. It is unlikely the relay is the cause since it acts a short when energized but you can swap it with the horn relay to rule it out. The horn, O2, A/C compressor and A/C condenser fan relays are all the same part number. You can do this next test with a voltmeter but a 12-volt test light would better. With good fuses in, battery connected and ignition OFF, remove the O2 relay and probe pins 1 and 3 to ground. With the key OFF pin 1 should be hot and pin 3 not. With the key ON pins 1 and 3 should both be hot. If a test light illuminates at pin 1 without blowing the fuse you have proved the circuit good to that point. Assuming the relay is not the problem, you have isolated the problem to circuitry south of the relay. Since you did not get a "beep" on pin 2 you can assume the O2 wiring is not shorted to ground. That's a good thing. My guess is that one of the O2 heater elements is shorted. That won't show up with your meter because the PCM cannot complete the circuit if the battery is disconnected (see O2 schematic above). If you have voltage to the relay and the relay is good your next step is to unplug all 4 O2 sensors and drive the car. If the O2 fuse does not blow, one of your O2 sensors is bad. Reconnect one sensor and drive the car. Check the fuse. If not blown, reconnect another sensor, drive the car, check the fuse. Repeat until you find the faulty sensor.