ground problems with 98 PCM?
04-17-2015, 04:13 PM
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ground problems with 98 PCM? I have a LS1 crate motor with an 98 PCM in my vette that was installed around 2000. It was one of the first LS swaps into a C3 vette. The motor was installed but never fired until I wound up with the car a couple of years ago. We rebuilt the car and hooked up a few wires and it ran, but it is running really rich. I need to get into the PCM to tune it, but HP tuners will not hook up.
The problem is that several people wired it before me and I am trying to go back through and find out where everything is supposed to go. I found one big problem with the PCM grounds leading to something that was not grounded. Once I resolved that, I am closer to getting into the PCM, but it fails when HP tuners gets to the part to "read entire VCM"
I know the 98 is an odball year and I have a 2002 PCM here that I may repin and try. I have actually labeled all the wires already and can repin the plugs. I just want to make sure that I have everything right before I get into that.
My question is about the other grounds. There is at least one pin out that is labeled PCM GROUND JUMPER. (blue 24) It looks like it is just going to a common ground on the engine block with everything else. Does anyone know if that is correct? I am also looking around and cant find a ground strap to the engine block. I do have continuity between the frame and the block, so it is picking it up somewhere, but if there is no strap, I am wondering how good it is. I am thinking about running a solid ground from the battery to the PCM as I know that electronics are sensitive to poor grounding. Good idea?
Another quirk I found in the wiring is that there is a wire coming out of the PCM in a slot that is labeled as unused. It is running to the alternator and I assume it is the exciter wire, but have not confirmed that. It is measuring about 9.8 volts at the pin with ignition on when I unhook the clip from the alternator.
Sorry for the noobie questions. Like I said the car is running and I drove it all last summer, but I need to get it running right. Hoping to be on power tour again in a few weeks. (yikes) I can read the sensor values on my iPod like O2, water temp, intake temp., etc. with an OBD2 dongle, but HP tuners cant validate the box to talk to it.
Any help would be appreciated
The problem is that several people wired it before me and I am trying to go back through and find out where everything is supposed to go. I found one big problem with the PCM grounds leading to something that was not grounded. Once I resolved that, I am closer to getting into the PCM, but it fails when HP tuners gets to the part to "read entire VCM"
I know the 98 is an odball year and I have a 2002 PCM here that I may repin and try. I have actually labeled all the wires already and can repin the plugs. I just want to make sure that I have everything right before I get into that.
My question is about the other grounds. There is at least one pin out that is labeled PCM GROUND JUMPER. (blue 24) It looks like it is just going to a common ground on the engine block with everything else. Does anyone know if that is correct? I am also looking around and cant find a ground strap to the engine block. I do have continuity between the frame and the block, so it is picking it up somewhere, but if there is no strap, I am wondering how good it is. I am thinking about running a solid ground from the battery to the PCM as I know that electronics are sensitive to poor grounding. Good idea?
Another quirk I found in the wiring is that there is a wire coming out of the PCM in a slot that is labeled as unused. It is running to the alternator and I assume it is the exciter wire, but have not confirmed that. It is measuring about 9.8 volts at the pin with ignition on when I unhook the clip from the alternator.
Sorry for the noobie questions. Like I said the car is running and I drove it all last summer, but I need to get it running right. Hoping to be on power tour again in a few weeks. (yikes) I can read the sensor values on my iPod like O2, water temp, intake temp., etc. with an OBD2 dongle, but HP tuners cant validate the box to talk to it.
Any help would be appreciated
