PCM issue
Thread Starter
Joined: Apr 2007
Posts: 39
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From: Los Altos/San Luis Obispo, CA
PCM issue Just completing an LS1 swap into a Miata race car and I'm having PCM issues.
When I hit the ignition on, nothing happens. I have unplugged the fuel pump relay and checked C2 Pin 9 (dark green/white) and it is not getting any signal to turn on. When trying to connect to the PCM with HP tuners, I get an error "Unable to locate VCM. Verify cable is connected and key is in the RUN position."
I have checked to make sure....
the following pins are grounded on both C1 and C2: 1, 40
the following pins have constant +12: C1 20, C1 57
the following pins have ignition +12: C1 19
OBD2 port has pin 4 and 5 grounded, pin 2 to ecu, and pin 16 to constant power.
What have I forgotten about?
When I hit the ignition on, nothing happens. I have unplugged the fuel pump relay and checked C2 Pin 9 (dark green/white) and it is not getting any signal to turn on. When trying to connect to the PCM with HP tuners, I get an error "Unable to locate VCM. Verify cable is connected and key is in the RUN position."
I have checked to make sure....
the following pins are grounded on both C1 and C2: 1, 40
the following pins have constant +12: C1 20, C1 57
the following pins have ignition +12: C1 19
OBD2 port has pin 4 and 5 grounded, pin 2 to ecu, and pin 16 to constant power.
What have I forgotten about?
Just completing an LS1 swap into a Miata race car and I'm having PCM issues.
When I hit the ignition on, nothing happens. I have unplugged the fuel pump relay and checked C2 Pin 9 (dark green/white) and it is not getting any signal to turn on. When trying to connect to the PCM with HP tuners, I get an error "Unable to locate VCM. Verify cable is connected and key is in the RUN position."
I have checked to make sure....
the following pins are grounded on both C1 and C2: 1, 40
the following pins have constant +12: C1 20, C1 57
the following pins have ignition +12: C1 19
OBD2 port has pin 4 and 5 grounded, pin 2 to ecu, and pin 16 to constant power.
What have I forgotten about?
When I hit the ignition on, nothing happens. I have unplugged the fuel pump relay and checked C2 Pin 9 (dark green/white) and it is not getting any signal to turn on. When trying to connect to the PCM with HP tuners, I get an error "Unable to locate VCM. Verify cable is connected and key is in the RUN position."
I have checked to make sure....
the following pins are grounded on both C1 and C2: 1, 40
the following pins have constant +12: C1 20, C1 57
the following pins have ignition +12: C1 19
OBD2 port has pin 4 and 5 grounded, pin 2 to ecu, and pin 16 to constant power.
What have I forgotten about?
It sounds like the PCM isn't coming on at all.
Start isolating components and testing them. You already got multimeter and/or test light and made sure that you have power directly at the +12v connector pins, right? Also, you used a continuity tester to make sure all of the appropriate connector pins have continuity with ground directly at the connector pin, right?
If that's the case and it all checks out, get a PCM wiring diagram and carefully verify that there are no other pins that need +12v or ground to turn on the PCM. If you need a wiring diagram, PM me.
If that doesn't turn up any issues, consider getting a battery and some small jumpers and connect the PCM to +12v and ground directly from the battery. (After you turn on the PCM, quite a few circuits should turn on, which you'll need to verify by touching a test light to the appropriate PCM pins.)
If the PCM still won't turn on, consider finding a different PCM to test.
That's my "divide and conquer" approach, which has served me well over the years. Let us know how it goes!
Start isolating components and testing them. You already got multimeter and/or test light and made sure that you have power directly at the +12v connector pins, right? Also, you used a continuity tester to make sure all of the appropriate connector pins have continuity with ground directly at the connector pin, right?
If that's the case and it all checks out, get a PCM wiring diagram and carefully verify that there are no other pins that need +12v or ground to turn on the PCM. If you need a wiring diagram, PM me.
If that doesn't turn up any issues, consider getting a battery and some small jumpers and connect the PCM to +12v and ground directly from the battery. (After you turn on the PCM, quite a few circuits should turn on, which you'll need to verify by touching a test light to the appropriate PCM pins.)
If the PCM still won't turn on, consider finding a different PCM to test.
That's my "divide and conquer" approach, which has served me well over the years. Let us know how it goes!
