I've been nailing down a crank no start condition for the last week or so. I've now isolated the problem to the ignition coil relay circuit. It's a pretty specific problem so I feel I need to give some background info, it's a bit lengthy but bear with me.
Basically, the relay is not properly receiving the signal from the PCM to activate the coils. I verified this by taking out the relay and jumping the 1 and 2 terminals with a paperclip - coils got voltage and car started up just fine (and yes I tested the relay too, it has not gone bad)
On my car, the number 6 pin on the PCM connector A has a green wire that runs to the fusebox and eventually connects to Terminal 3 on the relay. This wire is how the PCM sends the signal for the relay to switch on. I tested for continuity along this wire - all good. Before suspecting a faulty PCM, I also checked for continuity from Terminal 3 on the relay to body ground...and sure enough there is, with about 400 ohms resistance (if that matters). According to the FSM, any continuity here means there is a short to ground somewhere on that green wire. However, after opening up the wire harness and examining the full length of the green wire, I could not find any signs of damage or shorts.
Am I just not looking closely enough? Am I wrong to assume the continuity test proves there is a short to ground? The only place left I can think of is inside the fusebox itself - somewhere between where the green wire comes in and the relay's Terminal 3. But of course that part of the fusebox is all sealed up so I can't check it out without damaging the box, and its specifically designed to prevent shorts etc., so is that even a reasonable assumption? I'd be happy to get a new fusebox instead of a new PCM, but I'd like to know for sure before I go replacing parts. Is it possible for a short-to-ground to develop inside the sealed portion of the fusebox, seemingly overnight?
Feel like I'm losing my mind after chasing down this electrical issue for so long, just need a steady head to tell me if I'm on the right track or not, and what other checks I can do to be sure of my short-to-ground theory. Or, to tell me I'm all wrong and it is indeed a PCM fault. Any help/tips/opinions is much appreciated
Basically, the relay is not properly receiving the signal from the PCM to activate the coils. I verified this by taking out the relay and jumping the 1 and 2 terminals with a paperclip - coils got voltage and car started up just fine (and yes I tested the relay too, it has not gone bad)
On my car, the number 6 pin on the PCM connector A has a green wire that runs to the fusebox and eventually connects to Terminal 3 on the relay. This wire is how the PCM sends the signal for the relay to switch on. I tested for continuity along this wire - all good. Before suspecting a faulty PCM, I also checked for continuity from Terminal 3 on the relay to body ground...and sure enough there is, with about 400 ohms resistance (if that matters). According to the FSM, any continuity here means there is a short to ground somewhere on that green wire. However, after opening up the wire harness and examining the full length of the green wire, I could not find any signs of damage or shorts.
Am I just not looking closely enough? Am I wrong to assume the continuity test proves there is a short to ground? The only place left I can think of is inside the fusebox itself - somewhere between where the green wire comes in and the relay's Terminal 3. But of course that part of the fusebox is all sealed up so I can't check it out without damaging the box, and its specifically designed to prevent shorts etc., so is that even a reasonable assumption? I'd be happy to get a new fusebox instead of a new PCM, but I'd like to know for sure before I go replacing parts. Is it possible for a short-to-ground to develop inside the sealed portion of the fusebox, seemingly overnight?
Feel like I'm losing my mind after chasing down this electrical issue for so long, just need a steady head to tell me if I'm on the right track or not, and what other checks I can do to be sure of my short-to-ground theory. Or, to tell me I'm all wrong and it is indeed a PCM fault. Any help/tips/opinions is much appreciated
