1999 Chevrolet Silverado 1500 - Transmission leads to electrical issues

Started with me thinking we needed a new transmission. our truck has 220,000 miles and we have used it to tow. It would occasionally get stuck in 3rd gear. Took it to get a new transmission put in, the mechanic told me if I did it would still have the same problem since if he pushed on the instrument cluster, it would shift correctly. So, I pulled the cluster out and sent it in to be rebuilt, I also removed the cover on the steering column and found the set screw was super loose on the shifter, also, the wire for he tow button was severed (haven’t fixed that yet) plugged in the beautifully rebuilt cluster, turn on the key and it lit up nicely. Then I started the engine and everything shut off. all the lights went out and the guages flattened out. that is where you guys come in…where do I go from here? On another note, it may or may not be connected, the key fob stoped working, bought a new one…that one doesn’t work either. Pluged in an engine annalizer…nothing…won’t come on at all. so I am thinking electronics. Any and all help is very appreciated.

I don’t understand how the IPC (instrument panel cluster) has anything to do with transmission operation. The IPC is strictly a display device, it doesn’t control anything. All transmission shift control is done through the PCM.

When you say that everything shut off after starting the engine, does that refer to everything on the IPC only, or did the engine shut off too? What are the symptoms now? Does the engine still crank and run?

If something shorted out in the newly rebuilt IPC, fuses would be the first things to check. The left dash fuse block fuses labeled IGN 0 and IGN 1 are the main power supplies to the IPC (they also feed other things). The CRUISE fuse in the left dash fuse block, and the RADIO fuse in the underhood fuse block also supply power to the IPC.

Do the door locks work with the buttons on the doors? If not, there could be bad fuses for those too. There are 4 different fuses in the left dash fuse block for the door locks. If only the keyless entry doesn’t work, that could be a bad TBC fuse in the underhood fuse block, a bad keyless entry receiver, or a bad BCM, assuming the fobs are okay.

When you say you “plugged in an engine analyzer”, do you mean a code reader or scan tool being plugged into the DLC? If so, and it doesn’t power up, check the CIGAR fuse in the underhood fuse block. This fuse supplies the power to the DLC and the lighter in the dash. I’ve seen a case where the lighter in a Silverado shorted out and blew the fuse.

I wouldn’t expect all these fuses to blow. If many of them are bad, or if they are good but are not getting power at the fuse blocks, then there may be a more serious power problem.

Hi Bugmenot… thank you for all of the information! I wish I had been more clear.
I am not sure what a PCM is, but I will find out. I had 2 mechanics say it was to the IPC.

The IPC comes on perfect when you turn on the key, but as soon as you start the engine (which still runs fine) the panel loses power. Turn off the engine and keep the key in the one position and the power come back on.

The door locks and windows are fine, I will try to find the fuses for the keyless remote as the fob I have is new and has a new battery. I don’t know what a BCM is…LOL

Yes code reader, check on that fuse as well. Kind of sounds like I need a mechanic that specializes in electrical issues. :slight_smile:

kind regards

buy one of these:

Amazon- Dorman 1999 Chevy Silverado Shifter lever
(you don’t have to buy it off of Amazon or event that brand. I have used that one and it is working well.)

While I’m not sure this is your issue, that broken wire in the steering column could feasibly be shorting out and playing havoc with the transmission knowing when to shift. Mechanic pressing on the dash, could be moving the broken wire to ground/not ground. You know this is an issue, so start there.
It’s not hard to swap out, and you may even be able to reroute the wire so it won’t break again in the future.

Also, pull back out your cluster and make sure connections are tight and not getting snagged on anything.

PCM- is Personality Control Module
BCM- is Body Control Module

I’ve been poring over the electrical diagrams and can’t figure out how having the engine off or running could affect the power to the IPC. The problem could be with the ignition switch itself, perhaps not making good contact on the IGN 0 circuit after returning to the run position from the start position. In fact, there was a TSB (Technical Service Bulletin, number 01-07-30-002D) issued in 2004 regarding the ignition switch. Symptoms included a non-functional IPC and/or the transmission defaulting (or getting stuck in) second or third gear. For the heck of it, when it acts up after starting the engine, try jiggling the ignition switch to see if anything happens. If nothing happens, try checking the voltage at fuse IGN 0 while the IPC is inoperative. If there is no voltage, the ignition switch (or something in that circuit) is likely the problem.

The P in PCM is for Powertrain. The PCM is the main computer that controls the engine and transmission. I would hope it wouldn’t control your personality, though some people do seem to change personality when they get behind the wheel. :astonished:

you are correct. I had an old (now,) International that had a Personalty Control Module, and that is where my brain went first. :slight_smile:

Wow, you guys are amazing… thank you so much for all your help. I will start with a new shifter handle and yes, there is a flicker on the panel when you jiggle the keys, so a new one of those puppies too. I will try to keep my P nice and calm :smile:

Hi guys, replacing the CIGAR fuse made the IPC work and the code reader as well. We fixed the wire for the tow/haul button so that is working. When we plugged in the code reader, we got a code 1860 which looks like it is a TCC PWM Lock Up 3-2 Downshift Solenoid. So…looks like we need to order one of those :slight_smile:

I almost forgot, the fuse for the ING 0 was bad, so we replaced that one as well.

I’d wait a bit before ordering that. DTC P1860 is for the TCC PWM Solenoid Electrical Circuit, which doesn’t necessarily mean a bad solenoid. The bad IGN 0 fuse could have caused that DTC to be set. The code should clear itself after three trips if all is okay. If you cleared the code and it has come back, then consider further diagnosis.

I wouldn’t expect the CIGAR fuse to have any effect on the IPC. It’s totally unrelated. The IGN 0 fuse is one of the power supplies to the IPC, as well as the power supply to the transmission solenoids.

Is the IPC working perfectly now? The ignition switch seems okay? Keep in mind that the ignition switch was a known problem and, even if it seems okay now, it could be on its way out.

1 Like