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Neighbor and I have matching 2001 24V 4x4 HO 6 speed trucks. Axle ratio and paint color are only difference. Both are bone stock, his has 150,000 or so miles, mine has 440,000 and has been run much harder.

 

About a month ago, he sent me some DTC's he pulled with the Key. They were:

 

ECU 343, 1475, 577, 1286, 123.

 

Truck has dead pedal and resorts to idle only at times. I checked alternator, VAC voltage with Fluke DVM is 0.023 VAC at idle, rising to 0.031 at 2000 rpm on road. (I have the one with the detach wireless screen.)

 

2 weeks later, codes were:

 

ECU 118, 113, 606, 577, 343, 1475, 1286, 123.

 

Went into ECU harness, found wire #11 rubbing the clamp and corroded. Repaired the wire with a proper splice and heat shrink, he ran the truck about 200 miles, and then we have 

ECU 343, 1475, 577, 1286, 123.

 

He idled it over into a free stall in my lean to, and I put his ECM on my truck. His ECM won't drive my pump as hard (I think mine was Smarty tuned or something 10 years ago, haven't really done much but change oil and put fuel in it.). The truck is a little slower, but other than that, no major issues. Ran his ECM about 250 miles or so, and pulling back into my driveway, it hiccuped a hair, threw a ECU 121 code, and sputtered a bit. Gonna run it a bit more, but not sure what that was about. 

 

Ideas? I run a Scan Gauge on my truck, freeze frame data showed the TPS at 56% when the 121 code went active. No other issues. I was leaning towards ECM dying, but it just runs too good on my truck. Thinking he has a wiring harness issue somewhere else or a dying sensor, but everything ohms out ok when I'm looking at it. 

 

 

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I would pull the codes via an actual code reader and not rely on the key trick.

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Codes pulled with key, and then I verified them with a OBDII code puller later.

 

32 minutes ago, deereman01 said:

I checked alternator, VAC voltage with Fluke DVM is 0.023 VAC at idle, rising to 0.031 at 2000 rpm on road. (I have the one with the detach wireless screen.)

 Does this not constitute checking the alternator for AC noise?

 

Also, why does his ECM have different codes when bolted onto my truck? he never had a 0121 code before, and none of the others came up when it was on my truck?

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I would swap it back and see if it acts the same as before on his. Could be a bad joint in the ECM that got knocked in place during the swap. When mine went I would get different codes every time I read them. 

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6 minutes ago, dripley said:

I would swap it back and see if it acts the same as before on his. Could be a bad joint in the ECM that got knocked in place during the swap. When mine went I would get different codes every time I read them. 

That's an idea. I could see something like that happening. Say however, that I put his ECM back on his truck, and the ECU 343, 1475, 577, 1286, & 123 are back active. What advanced diagnostics steps would the rest of you take? 

 

Reason I'm asking, I didn't realize the cruise on the 2001 manual doesn't use the TPS at all. It's 100% fly by wire between the (whatever runs the cruise) and the ECM/VP44. This was new to me, cause I thought they used vacuum and the APPS. I learned something completely new after reading on this last night.

 

When his truck throws those 5 codes, it kicks the cruise off and dead pedals for an indeterminate period of time. What correlation do those sensors have with 5V power? I've heard that all 5V sensors on this engine use the same source, but then I see multiple sensor grounds and different sensor voltage sources. (All data taken from the Ram factory service manual, but I may have misread, feel free to correct.)

 

 

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Nunhttps://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/

Here is a list of DTC s with diagnostics.

 

I have the fly wire also. I believe the PCM is involved also. I believe it sends the speed signal to the ECM for to regulate the cruise. I do not know this for sure though.

 The sensors share a common ground in the engine wiring harness near the ECM connector. Not sure how the 5v power supply works. I do know this, we are in an area that I am not good with. Electronics is my weak spot. I am learning but have a long way to go. Hopefully folks more versed in this than I can add to this.

 

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On 4/11/2018 at 3:08 PM, deereman01 said:

Also, why does his ECM have different codes when bolted onto my truck? he never had a 0121 code before, and none of the others came up when it was on my truck?

This could explain the P0121,  Be sure to perform APPS Sensor calibration after the ECM swap.

 

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The P0577 code ( Cruise Control Switch Voltage High) may be just coincidental.  If the tilt wheel is used a lot, the wires that feed the cruise control switch flex over time and break internally.  It is easy to check and repair - just remove the plastic panel under the upper steering column to gain access.  The wire insulation may be intact, but the wire strands will be broken if this is the issue.  This has happened to my truck twice, now.

 

- John

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I have an update. 

His ECM started throwing the same codes on my truck that it was on his. the 577, 1475, etc. Swapped back to my ECM, ran it about 750 miles over the weekend, no issues whatsoever. Contacting a recommended ECM rebuilder now. Also will check under his steering column for stretchy wires. Will report back after I get his ECM on his truck and running. 

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ACS just emailed me after repairing the ECM. It's on the way back, and here are their tech notes.

 

Tech Notes:
We want to inform you that the ECM that was sent in only does engine functions ( we can not assist with the cruise control issues as for the functions are in the this ECM. Your cruise control, is controlled by the PCM which is located on the firewall (below is attached schematic where the PCM is located). Please refer to our website www.autocomputerspecialist.com for service for your PCM should you need it.  
 
Our findings:
You unit came in shorted out, your... wait to start circuit, APP pedal, CPU were all in short all was replaced and repaired as well as your pins were reflowed. ( your engine wiring harness is in short!!!
 
What must be done prior to installing repaired unit:
You must have repaired your wiring harness, battery and terminals replaced. All short in truck must be repaired. Make sure all parts replaced are OEM (mopar) parts are a MUST! All Problem in truck must be tended to prior to installing repaired unit ( failing to do so will result in shorting out the unit and it will not be covered under warranty.
 
What ideas do you guys have to check before reinstalling the ECM. No major issues were found with wiring shorted to something, but we could have other issues. Do I need to pull the engine harness off the truck?
 
Anyone with some sound technician advice here?
 

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ECM is back on truck, I cranked it after load testing all the wires and such. All wires load tested correctly. The only code active now is a P0341. This mean camshaft sensor issue. Camshaft voltage is only 3.8 volts. I understand that it's supposed to be 5 volts, and also understand this could equal week or no signal. 

 

I have 2 options. 

1) Send ECM back to ACS, and tell them about the issue.

2) I can only find wires 3&4 that supply the 5V to camshaft position going to camshaft position. Is this correct? I could add a buck boost circuit to the 3&4 wires between the ECM and the sensor, and this would bring it up to 5V.

 

Thoughts on each?

 

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Just wanted to do a final update on this. Truck has been a daily driver for 90+ days now, no issues. ECM was bad, had it rebuilt over in Florida. The other issues were due to half broken wires in the tilt column, which were repaired. The other issues with low sensor voltage were associated with bad battery cable connections, because after I cut off the original ends, and installed new lugs and military ordinance connectors on the batteries, we've had no further issues. Thanks everyone for the help, and maybe this will help someone in the future. 

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