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Can the cam position sensor be tested with a DMM for the correct resistance?  If so, what should the value be?  This is on an 01 2500 auto.  Trying to track down what's causing a P1488 code among others.  The trouble-shooting procedure tells us to replace the cam position sensor but we've done that a couple times.   Any help would be appreciated.  Thanks.

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Truck runs but not well.  Tach does not work.  Will not build more than 10PSI of boost.  CEL is on.  Has 7 codes total but seems that most if not all can be attributed to that 5V required for the WIF, Oil pressure, cam position and map sensor.  Codes are P1693, P0236, P0522, P0341, P1488, P0342 and P1295.  

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Have you cleared the codes since the cam sensor install to see what comes back? It does sound like the 5v circuit is corrupted. could be another bad sensor, wiring harness or the ECM doing it. We will need more help than my electrically challenged arse has. I had a similar experience back in 2010 when my ECM failed. Lots of codes on the sensor both high and low voltage with diagnostics telling me to replace then all. Mine had a mind of its own and was undriveable though. 

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On 6/6/2020 at 9:41 PM, jw9424 said:

Can the cam position sensor be tested with a DMM for the correct resistance?  If so, what should the value be?  This is on an 01 2500 auto.  Trying to track down what's causing a P1488 code among others.  The trouble-shooting procedure tells us to replace the cam position sensor but we've done that a couple times.   Any help would be appreciated.  Thanks.

Do you know anyone with a diagnostics box with a scope like the new snap on ones. I have a SO Modis Ultra and testing 3 wire sensors is easy using the scope as you spoon into the signal wire but a DMM won't read pulse width signals unless it has a scope

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Is your oil pressure sensor one wire or more, if more I would start there. It can have internal short messing with 5 volts. Otherwise could be in harness like @dripley said. WT mod takes care of a lot of it and there are few more spots check. 

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Update:  Everything we tested seemed to point towards a cam position sensor but after swapping it out twice, the voltage was never right after plugging in the cam sensor.  Had an electrical specialist look at it and they were able to confirm it’s the ECM causing this.  Said the vref signal was not supplying enough current with all sensors plugged in. They quoted me north of $2k to fix it.  I see on here guys have used Autocomputerspecialist.com with success having their ECM repaired so unless someone has a better idea, I’ll be sending mine off and hope for the best.  

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ACS is the one to send it to, they can test and fix 

As a thought though it might be worth checking continuity/ resistance on all sensor supply wiring yourself as it could be bad connection/corrosion or another bad sensor on the 5v, thats if you've not done so already.

Another thought is Snap On do a sensor tester that can supply any voltage from 0 to 8v, if you know anyone with one you could remove your 5v sensor supply pin from the ecm plug and feed that circuit 5v. This would probably throw a code because the pin is removed but if it is the ecm your present code should be erazeable This tester is not a huge amount of $

Mine was £90 from SO

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  • 3 weeks later...

Well the ECM is back from ACS. There are stickers on this thing saying the truck has a short in it.   We’ve already checked for a short to ground on the 5v circuit and didn’t find one.  Something else we need to check?  We did however end up having to have the alternator rebuilt after getting it checked during this process.  Is it possible that bad alternator took out the ECM 5v reference?  

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3 minutes ago, jw9424 said:

Is it possible that bad alternator took out the ECM 5v reference?

 

Yes. Its very possible. Still have the alternator retested before leaving the rebuilder. 

 

I've seen a 6.7L Cummins with weird issues with electrical which I had to walk away from because I couldn't figure out what went wrong. The ECM was rebuilt by ACS as well and ECM was labeled the same way. Checked all the wiring they asked for and then hooked up and it started and ran for 5 miles and died. Sent the ECM back and had it tested again. No problems with the ECM. Hooked it up and started and ran for 30 seconds and then died again. The owner was going to just buy a salvaged loom.

 

Now ACS does have a wiring loom rebuilder too so if the harness is the problem you can send the engine loom to ACS and they will test and rebuild the loom for you. 

 

 

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