boydchr

I have an '04 Silverado 1500 LS with what I believe to be an electrical problem that I can't trace. It started as intermittent but now is a hard fail. In the intermittent phase it would sometimes leave me stranded for up to four days and then decide to start and run for several weeks. In the hard fail phase it has not been drivable since May 2nd. Here is what I have done since May 2nd:

• Replaced the ignition switch (I am positive it is installed correctly)
• Replaced the blower resister (thought it could be involved because the blower stopped working on May 2nd as well)
• Tried a replacement PCM that gave the same results
• Checked all fuses and voltages
• Checked grounding points that I could get to
• Truck has a new starter that I replaced during the intermittent phase
• The battery has tested good multiple times.

On May 2nd I was running the A/C and turned the truck off with the A/C still on, what I consider a bad habit that I developed the last few years. A couple of hours later started the truck and the blower would not work, the MIL, ABS and Brake warning lights were on. Tried driving and the truck barely moved. Shut it off and started it back up with the same symptoms. Did limp it home and barely got it up the driveway. Read the codes and got
P0740, P0783, P0785 and a couple of others all referring to the transmission. Research said that all these codes together normally pointed to the ignition switch. Only other real symptoms are low voltages at the I/P fuse block and when you try to start the truck it just bumps the motor or nothing at all. If the motor bumps and you keep the key in the start position it will bump, wait a few seconds and bump again and keep repeating the cycle. I can force it to start using a remote start switch in combination with the key start but the truck will not move because the transmission electronics are not getting energized. I am current driving my dad's '05 Sierra and have been using it as a troubleshooting reference and found this at the I/P fuse block:
<table width="447" style="width: 336pt; border-collapse: collapse;" border="0" cellspacing="0" cellpadding="0"><colgroup><col width="77" style="width: 58pt; mso-width-source: userset; mso-width-alt: 2816;"><col width="93" style="width: 70pt; mso-width-source: userset; mso-width-alt: 3401;"><col width="92" style="width: 69pt; mso-width-source: userset; mso-width-alt: 3364;"><col width="93" style="width: 70pt; mso-width-source: userset; mso-width-alt: 3401;"><col width="92" style="width: 69pt; mso-width-source: userset; mso-width-alt: 3364;"><tbody><tr height="20" style="height: 15pt;"><td width="77" height="20" style="border: 0px black; width: 58pt; height: 15pt; background-color: transparent;"></td><td width="93" style="border: 0px black; width: 70pt; background-color: transparent;">

05 KEY OFF

</td><td width="92" style="border: 0px black; width: 69pt; background-color: transparent;">

04 KEY OFF

</td><td width="93" style="border: 0px black; width: 70pt; background-color: transparent;">

05 KEY ON

</td><td width="92" style="border: 0px black; width: 69pt; background-color: transparent;">

04 KEY ON

</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">SEO ACCY</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">12.37</td><td align="right" style="border: 0px black; background-color: transparent;">12.25</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">WS WPR</td><td align="right" style="border: 0px black; background-color: transparent;">0.01</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">12.37</td><td align="right" style="border: 0px black; background-color: transparent;">12.23</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">TBC ACCY</td><td align="right" style="border: 0px black; background-color: transparent;">0.01</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">12.37</td><td align="right" style="border: 0px black; background-color: transparent;">12.23</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">IGN 3</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">12.37</td><td align="right" style="border: 0px black; background-color: transparent;">1.63</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">4WD</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">12.37</td><td align="right" style="border: 0px black; background-color: transparent;">1.63</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">HTR/AC</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">12.37</td><td align="right" style="border: 0px black; background-color: transparent;">1.63</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">HVAC 1</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">12.37</td><td align="right" style="border: 0px black; background-color: transparent;">1.63</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">CRUISE</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">12.37</td><td align="right" style="border: 0px black; background-color: transparent;">1.63</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">BRAKE</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">12.37</td><td align="right" style="border: 0px black; background-color: transparent;">1.63</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">PDM</td><td align="right" style="border: 0px black; background-color: transparent;">12.49</td><td align="right" style="border: 0px black; background-color: transparent;">12.44</td><td align="right" style="border: 0px black; background-color: transparent;">12.37</td><td align="right" style="border: 0px black; background-color: transparent;">12.24</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">IGN 0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">12.37</td><td align="right" style="border: 0px black; background-color: transparent;">1.64</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">TBC IGN 0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">12.37</td><td align="right" style="border: 0px black; background-color: transparent;">1.64</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">VEH CHMSL</td><td align="right" style="border: 0px black; background-color: transparent;">0.02</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0.02</td><td align="right" style="border: 0px black; background-color: transparent;">0</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">LT TRLR</td><td align="right" style="border: 0px black; background-color: transparent;">0.02</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0.02</td><td align="right" style="border: 0px black; background-color: transparent;">0</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">LT TRN</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">VEH STOP</td><td align="right" style="border: 0px black; background-color: transparent;">0.01</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0.02</td><td align="right" style="border: 0px black; background-color: transparent;">0</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">RT TRLR</td><td align="right" style="border: 0px black; background-color: transparent;">0.02</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0.02</td><td align="right" style="border: 0px black; background-color: transparent;">0</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">RT TRN</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td><td align="right" style="border: 0px black; background-color: transparent;">0</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">DDM</td><td align="right" style="border: 0px black; background-color: transparent;">12.49</td><td align="right" style="border: 0px black; background-color: transparent;">12.44</td><td align="right" style="border: 0px black; background-color: transparent;">12.36</td><td align="right" style="border: 0px black; background-color: transparent;">12.23</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">AUX PWR 2</td><td align="right" style="border: 0px black; background-color: transparent;">12.49</td><td align="right" style="border: 0px black; background-color: transparent;">12.44</td><td align="right" style="border: 0px black; background-color: transparent;">12.36</td><td align="right" style="border: 0px black; background-color: transparent;">12.23</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">ECC</td><td align="right" style="border: 0px black; background-color: transparent;">12.49</td><td align="right" style="border: 0px black; background-color: transparent;">12.44</td><td align="right" style="border: 0px black; background-color: transparent;">12.36</td><td align="right" style="border: 0px black; background-color: transparent;">12.23</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">TBC 2C</td><td align="right" style="border: 0px black; background-color: transparent;">12.44</td><td align="right" style="border: 0px black; background-color: transparent;">12.44</td><td align="right" style="border: 0px black; background-color: transparent;">12.35</td><td align="right" style="border: 0px black; background-color: transparent;">12.23</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">FLASH</td><td align="right" style="border: 0px black; background-color: transparent;">12.44</td><td align="right" style="border: 0px black; background-color: transparent;">12.44</td><td align="right" style="border: 0px black; background-color: transparent;">12.36</td><td align="right" style="border: 0px black; background-color: transparent;">12.24</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">TBC 2B</td><td align="right" style="border: 0px black; background-color: transparent;">12.48</td><td align="right" style="border: 0px black; background-color: transparent;">12.44</td><td align="right" style="border: 0px black; background-color: transparent;">12.36</td><td align="right" style="border: 0px black; background-color: transparent;">12.23</td></tr><tr height="20" style="height: 15pt;"><td height="20" style="border: 0px black; height: 15pt; background-color: transparent;">TBC 2A</td><td align="right" style="border: 0px black; background-color: transparent;">12.48</td><td align="right" style="border: 0px black; background-color: transparent;">12.44</td><td align="right" style="border: 0px black; background-color: transparent;">12.36</td><td align="right" style="border: 0px black; background-color: transparent;">12.23</td></tr></tbody></table>

Bern

Looks like a bad circuit to the ign switch. check for power all time at the switch large red wire. test for power by back probing the terminal with key and all accessories ON

boydchr

Just checked. with the key off I have 12+ volts on both red wires at the ignition switch. Turn the key on and the red wire on the 3 prong side stays 12+ and the red wire on the 4 prong side goes to 1.55. I disconnect the ignition switch plug from the I/P fuse block and turn it on and 12+ remains on all wires except yellow which is for start. With the ignition switch connector pulled from the I/P fuse block it did start but I only let it run for a few seconds since I knew nothing else had voltage.


Right now it is starting on its own but the MIL and ABS lights remain on. The brake warning light will go off and then come back on. Put it in OD/D and it will not move, put it in 1 and it will so the transmission is still not getting enough volts to power its components. To be the ignition switch, the new one would have to have the same problem as the old (if the old had a problem) and the problem would have to be creating a large amount of resistance when a load is supplied to the output.


I did notice while it was running that the compressor kept kicking on and off. I pulled its fuse under the hood and it stopped but did not correct any other problems.


With the motor running the circuits with the low voltage drops to under 0.2 volts. I don't find bare wires anywhere and fuses aren't getting blown.

Bern

The 142 circuit has a large voltage drop. Said another way the circuit is not good enough to supply the power needed. You'll need to find the poor connection.


Check for loose burnt terminal in the C201connector located behind the instrument panel near the left side of the steering column and the Underhood fuse block C1 connector terminal B12. You'll need to release the block and remove it from the connectors.
You can also test the power in each place with connectors connected and accessories ON and another quick test is run a fused (about 30amp) jumper wire from the battery to the red wire terminal F of the Ignition switch.

boydchr

C201 connector looked clean but since I had it loose I put a dot of dielectric lube on all the terminals. B12 terminal in the C1 was definitely charred. Checked continuity through the connector and it was good so I cleaned the terminals and applied dielectric lube there on all those terminals. The best I got was a voltage increase to 1.95 volts. It's getting better, when I started the voltage was around 1.37. I'll try to do some more testing tomorrow evening.

boydchr

Started my daily troubleshooting back at the under hood fuse block connector C1 terminal B12. Getting a better look at it indicates it could still be the problem. I believe it needs to be replaced but so far I can't remove the terminal, appears to be fused to the connector. Hopefully there is a picture attached.

boydchr

Since I couldn't get the B12 terminal out I went to the dealer, they said they didn't have a listing for the C1 connector and tried to sell me what I believe was a new fuse block for $520. Went to one salvage yard and they said they would not allow the connector to be cut off and told me to go to their "Parts-U-Pick" yard to get it. Went to a different yard and they said if I went out and found it then cut it off myself they would sell it to me for $125. Went to the "Parts-U-Pick" yard and they gave me a list of possible vehicles and where in their yard I would find them and charged me $2 to go in. I cut two of them off since I was there. This yard is on the banks of the Arkansas river and all their cars were under water during the recent floods so they were having a half off sale with no refunds. I got the two connectors for $3.19, I might have to do some cleaning but the flood water didn't hurt them any.


I will start reassembling my truck Thursday evening. What I need to know is with the extent of charring and melting of my original connector, do I need to be looking for something that caused it? And if so where should I start the search? So far the only other thing I have found was the blower resister looked pretty bad and I replaced it.

Bern

This circuit is protected with a 40 amp fuse and the fuse wasn't blown. So I don't think the circuit is overloaded.


The best way to repair this is to replace the connector ( plastic part) with one of the replacements you now have.
You'll need to need to transfer all of the other terminals from the burned connector to the replacement except the burned terminal.
leave the terminal with wire installed in the replacement connector . Cut off the burned connector and attach to replacement B12 wire with butt connector, solder and shrink tube.
Also clean the fuse box terminal good and apply dielectric grease to both terminals.

boydchr

Thank you Bern for pointing me in the right direction and the information you forwarded to me, I may have never thought to pull the C1 connector on my own.


For anyone reading this thread, the problem was solved by replacing the plastic C1 connector on the under hood fuse block. The B12 terminal did break free and fall out of the original C1 connector. All it needed was a little more cleaning, a new home and a little dielectric grease. I put everything back together and took the truck for its first drive in almost two months.


Although not confirmed, I believe the underlying root cause started with the blower resistor which was also replaced. The blower was having intermittent problems for over a year and was getting worse just before the truck died.