Help With Spark
Thread Starter
Teching In
Joined: Jan 2025
Posts: 22
Likes: 0
Help With Spark I'm trying to get an 04 LM7 to run. I had it idling, but had no throttle. That turned out to be I had a 6 pin cable to the TAC instead of the 9. Before I figured that out, I was checking the wiring to the Throttle Body for breaks. Now I have that pedal cable swapped, and I can hear it moving the throttle body, but I don't have spark. I didn't make any other changes.
Before I make a bigger mess out of this, can someone please confirm what kind of power I should be seeing at the connectors for the banks of coils? I currently (pun firmly intended) see 12V from the pink to every other wire in the connector with the key in the run position. No other combination shows volts. Is that right or have I shorted something in that harness to ground? (my understanding is that spark is commanded by the PCM grounding but I don't know what it should look like in the run position)
Any insights massively appreciated!
Before I make a bigger mess out of this, can someone please confirm what kind of power I should be seeing at the connectors for the banks of coils? I currently (pun firmly intended) see 12V from the pink to every other wire in the connector with the key in the run position. No other combination shows volts. Is that right or have I shorted something in that harness to ground? (my understanding is that spark is commanded by the PCM grounding but I don't know what it should look like in the run position)
Any insights massively appreciated!
Thread Starter
Teching In
Joined: Jan 2025
Posts: 22
Likes: 0
OK, I've spent some time experimenting with a multimeter. I have continuity to ground at the ground pin on the coil jumper harness and on E, which is a brown wire which I THINK is the low voltage reference which should go to ground. No continuity to ground anywhere else, so it isn't a broken wire, voltage/ground to complete circuit is coming from the PCM.
Does that mean the PCM is bad or does that mean the PCM is ok and something else is wrong? I have RPM signal logging I crank, so that tells me the CPS is ok. Right?
Does that mean the PCM is bad or does that mean the PCM is ok and something else is wrong? I have RPM signal logging I crank, so that tells me the CPS is ok. Right?
Thread Starter
Teching In
Joined: Jan 2025
Posts: 22
Likes: 0
Bless you! This is what I've been trying to confirm!
So if those signal/trigger wires are not showing 5V when probed in connection with ground, but are acting as a ground when I probe them in connection with the 12V in (so I have a probe on the pink and a probe on the signal wire I see 12.xx V with the key in run) but they are not showing continuity with the ground, then the problem is probably in the PCM? (I'm probing the big connector that has all of the coil signal wires along with the 12V, ground, and low reference)
So if those signal/trigger wires are not showing 5V when probed in connection with ground, but are acting as a ground when I probe them in connection with the 12V in (so I have a probe on the pink and a probe on the signal wire I see 12.xx V with the key in run) but they are not showing continuity with the ground, then the problem is probably in the PCM? (I'm probing the big connector that has all of the coil signal wires along with the 12V, ground, and low reference)
