2003 Dodge R2500 Transmission Problem

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Tim Martin
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2003 Dodge R2500 Transmission Problem

Post by Tim Martin »

This Dodge Truck, a 2003 R2500 with a 5.9L diesel, 4wd, and automatic transmission has an issue. When it rains, the transmission will not come out of first gear. When the roads are dry and the sun is shining, the engine runs fine and the transmission shifts just perfect. Customer reports speedometer stops functioning intermittantly. The owner has had this truck to at least 3 or 4 other shops including a transmission specialist and it seems no one can figure it out. There is no trouble codes stored in the PCM. Where do I start in diagnosing this one?
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brianp87
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Re: 2003 Dodge R2500 Transmission Problem

Post by brianp87 »

Id start by replicating the issue. Honestly unless I could find a way to replicate it consistently then there is now way to guarantee the repair.
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ricmorin
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Re: 2003 Dodge R2500 Transmission Problem

Post by ricmorin »

Agreed. There is a clue. The speedo dropping out could give it away. If the speed signal was to lose integrity in the rain, I'd expect the transmission to shift improperly. I'd capture some known good waveforms (at the pcm) of the speed signal, then wait until it rains and take some more. The signal to the cluster comes over the PCI bus from the PCM. My suspicion is a short in the harness that needs water to complete the circuit.
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Re: 2003 Dodge R2500 Transmission Problem

Post by nickscarcare »

If you are trying to duplicate speedo dropping, get a garden hose and spray the speed sensor to see if anything happens. Also a spray bottle with some salt water helps big in finding issues, I like using it on plug wires to find little arcing.
Some people try to turn back their odometers. Not me, I want people to know why I look this way. I've traveled a long way, and some of the roads weren't paved.

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Tim Martin
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Re: 2003 Dodge R2500 Transmission Problem

Post by Tim Martin »

Ok, here is an update on this.

With the engine idling and the transmission in any position including park, the speedometer rockets wildly all over its swing from 0-120mph. Going down the road with my scanner hooked up and monitoring vehicle speed, it also does the same thing although not to the extremes as the dash unit does. Also, when I try and accelerate from a dead stop, the transmission is severely slipping and if I can manage to get it up to say 20mph, it trys to shift into second gear but then right back to first. It is constantly trying to shift into second gear. I went back to shop, shut engine off, a few minutes later I went out for another drive and this time the transmission shifted perfectly fine. I could press accelerator to the floor and it takes off like a rocket and everything except the speedometer is fine. Speedo is rocketing back and forth violently. Definitely a speed sensor issue or wiring. Yesterday when I was driving it was a nice day though so it does it more than rainy days which makes me wonder what all else might be wrong.
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Re: 2003 Dodge R2500 Transmission Problem

Post by Tim Martin »

Ok, here is another update.

I began by checking several things. With speedo wires disconnected from the output speed sensor, and the harness disconnected from the PCM, I ohms checked both wires for any continuity between them as well as checking for short to ground. Both are good. Speed sensor is new. With speed sensor disconnected or connected, driving makes no difference going down the road. I unplugged transmission relay from power distribution box, no difference. I removed fuse for ABS, no difference. As per service bulletin from MOPAR, someone had replaced the seals on the wiring harness's at the PCM due to rain intrusion there. At this point, I am highly suspicious of the PCM as the problem. Short of replacing it, is there any way of being sure that the PCM is the problem? Or is there any other things I should be checking?
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Re: 2003 Dodge R2500 Transmission Problem

Post by brianp87 »

Did you load test the wiring or just test continuity? Is the speed sensor reading accurately? Have you scoped the sensor during the failure?
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Re: 2003 Dodge R2500 Transmission Problem

Post by ricmorin »

Tim Martin wrote:Ok, here is another update.

I began by checking several things. With speedo wires disconnected from the output speed sensor, and the harness disconnected from the PCM, I ohms checked both wires for any continuity between them as well as checking for short to ground. Both are good. Speed sensor is new. With speed sensor disconnected or connected, driving makes no difference going down the road. I unplugged transmission relay from power distribution box, no difference. I removed fuse for ABS, no difference. As per service bulletin from MOPAR, someone had replaced the seals on the wiring harness's at the PCM due to rain intrusion there. At this point, I am highly suspicious of the PCM as the problem. Short of replacing it, is there any way of being sure that the PCM is the problem? Or is there any other things I should be checking?
With all due respect, ohming the wiring is not a particularly conclusive test unless there is an constant open, and we already know there isn't since it works most of the time. Disconnecting the speed sensor entirely is also not a conclusive test, as the PCM most likely has a strategy backup for just such a contingency. The only way you can CONCLUDE the PCM is faulty is to EXCLUDE any outside source. Again, I'd scope the speed signal at the PCM and start recording the waveform. When the vehicle acts up, mark the recording and review it. If there is no anomalous input to the PCM during the symptom, then it's reasonable to conclude the PCM is faulty.
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Re: 2003 Dodge R2500 Transmission Problem

Post by brianp87 »

How did you do on this?
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Re: 2003 Dodge R2500 Transmission Problem

Post by Tim Martin »

brianp87 wrote:How did you do on this?
Didn't get to the root of it yet. Backed it out so we could take a Duramax engine apart that had a bolt or nut go through the cylinder head and caused a misfire. Damaged head and piston.
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