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I'll keep this short to the point lol. I'm in a pinch to get my car up and running for this Sunday last race event. I got this code last Thursday/Friday and I have done the following:
Replaced cam sensor with new AC Delco. Still have the code
Tested Red pin at cam sensor harness plug for 12V...only have 6.6V Back probed Red Pin 39 12V+ cam sensor and I only see 6.6V at the PCM. Should be battery voltage
Back probed Lt Green Pin 2 12V+ crank sensor and I see 10-11V.
I unplugged the connector at the PCM and supplied battery voltage through the red wire for cam sensor 12V+ and did get battery voltage (Wiring is OK)
Below diagram references Blue/Red PCM but I confirmed the pins discussed are the same for Blue/Green PCM
@C5 Diag I'm sure you have a lot of people asking for your help so I apologize specifically dragging you in here. I would greatly appreciate any specific multimeter testing to also do.
I am picking up another PCM today at lunch to trial tonight as well in case it is the PCM is the issue.
Thank you!
Last edited by smitty2919; Oct 20, 2023 at 09:09 AM.
The cam and crank sensors share the same feed which is the orange wire at pins 20 and 57 through the PCM B fuse #23 at the PCM C1 connector….check both for system voltage…helped a member 4 years ago with low voltage (around 2 volts) at crank sensor…had him remove the CAM sensor connector and the 12 volts came back…shorted cam sensor bring down the 12 volts on crank sensor…I would check new cam sensor unplugged and see if you see 12 volts at pin 39 C2 connector….even new it can be BAD !!…I would also check PCM fuse 16 which is ignition feed at PCM…pink wire pin 19 C1 connector…check with key ON or start…be sure you are 100% correct on the wires you are checking.
Awesome will do! Thank you so much for the quick response!
6.6V was on the cam sensor plug red wire at with the sensor unplugged, PCM plugged in, KOEO
I'm PRETTY sure it was also 6.6V when I back probed red wire Pin39 on C2 also while sensor was unplugged. I will redo these tests to be 100%
I also plan to test Pink/Blk Pin 61 C1 ground circuit continuity for cam sensor. PCM connected, sensor unplugged.
Voltages taken at PCM by back probing wires KOEO and lead back to battery negative terminal:
Voltage at cam sensor power wire C2 Red #39 = 6.6V sensor unplugged / .121V sensor plugged in (new and old were the same reading)
Voltage at C1 orange #20 #57 = 11.4V for both
Voltage at crank sensor power wire C1 Light Green #2 = 10.53V
PCM Fuse #23 is OK
Ignition feed fuse #16 is OK
I have continuity between the cam sensor ground wire Pink/Black at sensor plug and Battery negative
Maybe worth mentioning that I had a E85 sensor power wire piggybacked off of the PCM fuse #23 (however everything had been working fine until last Thursday). It was a T-jumper that also maintained the PCM fuse. I since moved this power wire to fuse #15 for 02 sensors. All readings above is AFTER I moved the E85 sensor power wire and thus should be accurate.
I used this:
So the car will run once started but with cam sensor DTC. Which I assume means the crank sensor is OK?? Crank sensor power wire confirmed OK at ~10.5V
My next step may be to swap in the other PCM??
Last edited by smitty2919; Oct 18, 2023 at 06:15 PM.
You need the crank sensor to start…the cam sensor can be bad but will take longer for the engine to start !!….if you check for 12 volts at each sensor feed AT the PCM with sensors unplugged can be a bad PCM if all PCM power feeds are good.
It's strange, when I test voltage at cam sensor plug power wire I see 11.3V flash but then it jumps down to 6.6. Remove negative lead on battery and reapply it, it will flash 11.3V then down to 6.6V
It will eventually start and run after longer cranking...only 6.6V at cam sensor plug AND coming out of PCM seems to make the PCM the culprit.
It's strange, when I test voltage at cam sensor plug power wire I see 11.3V flash but then it jumps down to 6.6. Remove negative lead on battery and reapply it, it will flash 11.3V then down to 6.6V
It will eventually start and run after longer cranking...only 6.6V at cam sensor plug AND coming out of PCM seems to make the PCM the culprit.
I'll swap PCM now.
Let me know if that works...if not there is something I can have you check....disconnect the C2 Connector at the PCM and the cam sensor connector...take a 12 volt test light connected to battery positive,,,touch the test light to either end of the red wire at the PCM or at the Cam sensor...make sure test light doesn't light.
I have driven the car last 2 days to work. Everything seems to be OK.
In this situation, a new PCM was needed. If I can do more digging on how/why this happened I will report back. It seems odd that ONLY the cam 12V+ pin was affected and caused this issue.
I have driven the car last 2 days to work. Everything seems to be OK.
In this situation, a new PCM was needed. If I can do more digging on how/why this happened I will report back. It seems odd that ONLY the cam 12V+ pin was affected and caused this issue.
If you still have the old PCM and want to open it up and find where that 12 volt pin is you can check the circuit board…maybe you’ll find something.
If you still have the old PCM and want to open it up and find where that 12 volt pin is you can check the circuit board…maybe you’ll find something.
I troubeshooted a 1998 PCM two years ago on the cooling fan circuits .
The fans started with low speed as they supposed to do when cooling temp reached 219 but still the DTC P0481 was initiated .
I verified the PCM input was grounded by the PCM and energized both relays using my osciiliscope
I think parts of the internal ground path in the PCM circuits where damaged and caused this alarm
A new PCM was installed and the DTCP0481 was gone
I think inspecting the internal circuit and paths of this PCM could be interesting.
P0342 Cam Sensor "A" Circuit Low
