So my 2004 c5 developed a P0352 no spark cylinder 2. Used the diagnosis flow chart from gm posted on another thread. Tested everything annd made it to point where is said it was either the pcm or wiring to pcm. Got a new pcm that was programmed to the bin, did the security programming for key. The car ran fine at this point and fixed the issue of no spark on cylinder 2. The only issue was there was a P0315 which upon reading other threads I found it was because I swapped the pcm and crank sensors needed a relearn from scanner. Did the relearn which involves revving it out in neutral. After the relearn the problem came back and had no spark on cylinder 2. Any help is appreciated it. I’m kinda lost at this point. I feel like it may be a short to power or short to ground that burnt out the new pcm. But it’s just weird how it happened only after the relearn procedure.

 

Always helps if you include the year of your car in your sig.

 

added it into the post thanks

 

So the troubleshooting for that code only has you replace the PCM if no wiring/connections issues were found by inspection and measurement/ evaluation of the circuit(s). So the PCM is only replaced after the troubleshooting has led to that end. It does not sound like you exhausted the circuit(s) evaluation, and just went for the PCM

Also not familiar with P0315 on a 2003. Have seen on a 2004.

 

No definitely didn’t just throw a pcm in it. I followed the gm diagnostic flow chart for the issue. I’ll attach it bellow. It has you essentially test for power and ground on the coil connector with test light. Both checked out. Everything checked out and lead to “replace pcm”. Which fixed the issue. until the crank variance relearn that has to be done after a pcm is replaced was done. Car was driving fine after pcm replacement until I got around to taking it to shop with bi directional scan tool to do the relearn for crank variance.

 

Also have checked the measurements back probed at the connect with a DMM and compared to the other coil pack connectors that were a known good. And sorry that was a typo it’s a 04

 

So you have a P0352 and you replaced the PCM and now you have the same DTC ??…how EXACTLY did you check each of the 4 wires especially the IC “control” ??..I had a Forum member with a P0354 bring his car by and I found the control wire was shorted to ground.

 

I replaced the pcm and the issue was fixed. I verified that cylinder 2 was getting spark again, Test drove the vehicle, and check codes P0352 wasn’t a current code only in history. The only current code after pcm replacement was P0315. So I went and got the crank variance relearn done. Immediately after the relearn when I left the issue came back and P0352 was set with a misfire.

As far as testing before replacing the pcm. I started by using a test light. Tested ground circuit with test light hooked to battery voltage it illuminated. Then I moved on to next step of flow chart and did a drag test on the terminal ends and moved the wires back and forth little to test for intermittent issue. Even though it was a constant no spark. Next put my test light on battery ground and tested positive wire on coil pack connector also illuminated. Also used a multi meter to verify the power wire at the connector was getting full battery power even though it was lighting the test light. Then I tested the signal wire at the coil pack connector to pcm negative probe on chassis ground, positive back probed on connector. I belive this was measuring in hz and there was a range it needed to be in. It was on the low end but I belive it was within spec. This is only reading I don’t remember off top my head I can go measure it again if need be. Then after all this I believe the last step it called for was to measure continuity for the signal wire from the pcm connector to the coil pack connector. After that it said replace pcm. The only reading I didn’t do was the continuity test from pcm connector to coil pack connector for signal wire because it had a voltage reading and was within spec for hz reading.
Any help’s appreciated I can go back and do every test if someone’s willing help.

 

I had a Forum member bring his car by and he had a P0354 and I found the control wire shorted to ground…do you know how to check for a short to ground ??…he had the torque tube out and there is a clamp which couldn’t be reached which most likely had a frayed wire and without ripping everything back out so I bypassed the control wire…I cut the control wire at the PCM and at the connector above the valve cover and spliced in a new wire by soldering it in…we just bypassed that section of wiring.

 

No honestly not really. But if u could give me some guidance how to in this situation I could check it.

I’m kinda lost where to go with diagnosis at this point. After the new pcm fixed it then relearn made it come back. I kinda just chalked it up to a short to power or ground. And figured it burnt out the driver of pcm. But like I said any help is appreciated. And I can run most tests over again and provide the values of it, if it can help somone help me figure it out.

 

To do a “short to ground” test remove the PCM C2 connector and the coil pack connector…you will need an ohm meter set to its highest resistance scale…with both ends of the circuit disconnected place one lead of the ohm meter on either pin 67 on the PCM end or the red wire terminal on the coil pack end…now place the other lead of the ohm meter on a good ground (use the engine block)…anything other than “OL” or whatever your ohm meter shows when you hold the leads apart is what you SHOULD see…if you don’t see this you have a short to ground…even if you do show OL you may have to shake that harness down…you should have come here first and we could have saved you from replacing a PCM…they RARELY go bad !!

 

Thanks man means a lot. I’ll go ahead and do this tomorrow afternoon and post findings. And honestly I use this website a lot. But I’ve never made an account because I thought it wasn’t active anymore. The posts I always saw or used were alway so old lol. Good to know now though.

 

If you don’t know which is the C2 connector on the PCM just remove both connectors (DISCONNECT BATTERY FIRST) and connect one lead of ohm meter on the control wire at the coil pack and other lead on the engine block…if not OL you have a short to ground…it may be in the coil pack wiring harness so you have to check both at the coil pack and again at C110 which is the white connector between coil packs 4 and 6.

 

I was thinking just do the short to ground check between C110 and the coil pack connector…that way you don’t have to pull the connectors off the PCM…if good at the coil pack harness then go to the PCM !!

 

Sounds good I’ll check it out tomorrow. The control wire at c110 should be same color as control wire at coil pack connector right? Think last time I checked the pcm wire for each coil pack is a diffrent color. So in this case it will be red at c110 and at coil pack connector?

 

The control wire is RED from the coil pack to C110 and then it’s RED/WHITE from C110 to the PCM…look at the wiring diagram for #2.

 

Jacked car up took wheel off, then took battery out, took both pcm connectors off. Red probe on red wire of cool pack connector, and black to area of engine block. It was OL. Tested it on every range K, M, and regular ohms all showed OL. Also tried using different ground just to verify.

 

Since you have the PCM connectors off find the control wire and with the ohm meter see if you have continuity between the PCM and the red terminal on the coil pack…just want to make sure you don’t have an open in the circuit…if you have a 12 volt test light connect it to B+ and probe the BROWN Low Reference wire which is a computer ground…the test light should light…I would try to wiggle the harness down to find the short to ground or to find an open…to do a coil pack “functional check” turn the key on and back probe the red wire with the connector installed…remove the plug wire off the coil pack and keep it about 1/2 inch from the coil pack…with a 12 volt test light connected to B+ tap on the control wire…the coil pack should fire !!…video below on my 2008 but these 4 wire coil packs all operate the same way.

 

This is the voltage you will see on the control wire with the engine running…with a lab scope you will see roughly a 0-4 volt square wave…you may have a bad coil pack…if everything checks out good try swapping coil packs….yes, it may be a bad PCM but you want to make sure you’ve checked everything.

 

Sounds good I’ll go head give that a shot. My only questions are 1. dose it have be low impedance test light with the led, or will a normal test light be ok? 2. after I check continuity should. I put the battery back in and plug pcm back in aswell. I only ask cause I assume the brown low ref is grounded in pcm?