2003 Ram 1500 - OBD2 Won't Com but was...Crank No Spark
#11
Would not throw an crankshaft error.
#12
The 4.7 uses a 16 tooth tone ring for the crank sensor. Basically, it's a signal generator..... At some point though, they changed to a 32 tooth tone ring, and the two are just not compatible. Not sure what year that change happened though.
#13
#14
When we have the PCM unplugged for hours, when we try to start, I get it to fire a little bit as I'm getting some "POP POP POP" coming out of the manifolds. Then nothing.
I found a wire diagram for the camshaft sensor and crankshaft sensor and check 5V, Ground, and Signal. The cables checked out back to the connector on the PCM and none were shorted together.
So if 16 tooth, that means we get a trigger 22.5 degrees. With the cable plugged in, the key on, I am measuring 5V from Orange to Black, so I know there is power to the sensor. The signal wire is showing 5VDC, however, if I rotate the crank, we should see it go low or 0VDC. By moving ~1 degree, we saw the 5V drop to 0.27V but then quickly jump back up to 5VDC. We could rotate many degrees and never saw the signal stay low.
This tells me either the new crank sensor is bad, or the PCM is bad.
The bluetooth OBD reader has a live mode that shows RPM. To make sure it was working, I had it plot air-temp and throttle position. As I pressed the pedal, I could see TPS change. Air temp was also reading 50 degrees, which is the temp in my garage, so know it was working. RPM always read 0, so PCM is not reading the crank.
Questions:
- Do you still suspect a wire issue?
- Do you think the cranksensor is bad? We are going to go get another and give it a try.
- Do you think the PCM is bad and that is why the cranksensor signal output is stuck on 5V?
#15
Quick update to the above. Cam sensor does toggle 5V/0V/ Checked the crank sensor as sometimes we get RPM to show up on the scanner. I'm now seeing the cranksensor output toggle high-low and also triggers the fuel pump on that transition. Still no spark. With this weird behavior, do you think the PCM is bad?
#16
#17
Mfg date 10/2002
VIN: 1D7HU18N13S176681
PCM has 4 connectors.
we pulled the crank sensor and checked the ring. It has 16 teeth.
SN off the engine block: 53020661AE
VIN: 1D7HU18N13S176681
PCM has 4 connectors.
we pulled the crank sensor and checked the ring. It has 16 teeth.
SN off the engine block: 53020661AE
#18
Question: I'm want to order a replacement PCM. This looks to be the correct one: https://store.allcomputerresources.c...-computer.html
Based on the info above (VIN/Engine/PCM), does this look correct to you?
Based on the info above (VIN/Engine/PCM), does this look correct to you?
#19
Reading more, the eighth letter in VIN, M=16, N=32. This is N for 32. 4-plug PCM = 32, 3-plug =16. Maybe the smoking gun here.
If the old motor is 32-tooth and this one is 16-tooth, is there a way to make this motor work and how do we do that (I assume only way is to tear down, pull crank, swap ring and then pull front cover and swap cam gear)?
Thank you for your help so far, I really appreciate it. If any new comments based on the above, let me know?
Last edited by servocam; 11-22-2021 at 02:32 PM.