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Discussion Starter #1
2003 Dodge Ram 2500 5.7L
For a few months the ABS and Brake Lights on the dash were on, and while I was waiting for my service person to come back to work I started having problems with a power loss in the engine. The truck would lose power, but not shut down completely; and if I turned the key off and then back on, the engine would run for a while before doing it again. I checked for a code, and there were not codes, just the "lightning bolt" lighting up when the engine lost power.

I replaced the MAP sensor just to be safe, but this did nothing. I found a video no youtube where someone else had the same exact problem, which they resolved by replacing the throttle assembly. I bought & installed a new throttle assembly from the dealer and all was well for about three weeks, and then I started having the same problem again. Although some forums said the computer needed to be flashed after the throttle assembly replacement, I checked with the dealer and they said it was not necessary. I did not flash the computer, but did do a hard reset.

While I was still waiting to get the truck in the shop for the ABS and Brake Lights, I ran another code search and found codes P0700 - Transmission Control System MIL Request and P1794 - Speed Sensor Ground Error. In searching youtube I found two people who fixed the P0700 error code with a speed sensor replacement, so I went to the dealer and replaced my speed sensor as well. Unfortunately, this did not change anything and I still have the P0700 and P1794 codes....and when I was driving on the highway today, the truck lost power three more times.

Before I bite the bullet and take this to the dealer (rather than my local repair shop) does anyone have any idea what I can do to fix these problems? Any help would be appreciated.

Thanks.
 

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P1794 = Speed Sensor Ground Error. Check the ground circuit on the speed sensors. Both speed sensors share a common ground (that connects to and is grounded through the PCM). The trans temperature sensor also shares this same ground circuit. It connects to pin 13 on the C4 connector (end connector with green stripe or mark) on the PCM, pin 22 on the main trans wiring harness (solenoid connector), and pin 2 on each of the speed sensors (input and output speed sensors). Make sure there's not a broken wire or bad connection somewhere in that circuit.
 

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Both speed sensors are on the driver's side of the transmission case, right on the horizontal centerline. The input speed sensor is just behind the bellhousing; the output speed sensor is at the rear of the case, right in front of the extension / 4x4 adapter.
 

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On my 3/4 ton the rear speed sensor is in the side of the rear differential housing. That's what was wrong with my truck when the brake light and the ABS light came on. Mines a Cummins so I don't know if that makes any difference.
 

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On my 3/4 ton the rear speed sensor is in the side of the rear differential housing. That's what was wrong with my truck when the brake light and the ABS light came on. Mines a Cummins so I don't know if that makes any difference.
You have a different transmission than the 5.7L gas engine.
 

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Discussion Starter #7
P1794 = Speed Sensor Ground Error. Check the ground circuit on the speed sensors. Both speed sensors share a common ground (that connects to and is grounded through the PCM). The trans temperature sensor also shares this same ground circuit. It connects to pin 13 on the C4 connector (end connector with green stripe or mark) on the PCM, pin 22 on the main trans wiring harness (solenoid connector), and pin 2 on each of the speed sensors (input and output speed sensors). Make sure there's not a broken wire or bad connection somewhere in that circuit.

Thank you, again. I will be working on the truck this weekend. I have a service manual for the 2004 Dodge (my truck is a 2003) and was going to use that to find the PCM (although I think I know where it is) and follow the wiring diagram to locate the wires you specified. Of course, I am assuming the wiring is the same for the 2003 and 2004?
 

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Thank you, again. I will be working on the truck this weekend. I have a service manual for the 2004 Dodge (my truck is a 2003) and was going to use that to find the PCM (although I think I know where it is) and follow the wiring diagram to locate the wires you specified. Of course, I am assuming the wiring is the same for the 2003 and 2004?
In many cases, wiring is the same from year to year, but it's not something you want to take a chance on. Go to rambodybuilder.com and you can drill down through a set of PDF files to find the wiring diagrams, etc. for your specific truck.
 

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Discussion Starter #9 (Edited)
Update 10/18/14: My mechanic has returned and last Monday he ran a scan with his machine and found that the ABS/speed sensor on the front, left, wheel was bad. It was cheaper to buy the entire wheel bearing than just the sensor, so he replaced the wheel bearing and the P0700 and P1794 codes disappeared.

My ABS/Break lights are finally off....but I still have the problem with the engine going into "limp mode" (a description offered by another Ram owner with the same problem); and now I have two new codes" P2106 - ETC System Forced Limited Power, and P1618 - Sensor Reference Voltage error. Also, my scanner does not see these new codes, so they may have been there right from the beginning.

So far I have replaced the throttle control body, MAP and IAT sensors, rear speed sensor and front ABS/speed sensors, although I think the speed sensors were tied to my ABS/Brake issues, and not the "limp mode" problems.

My mechanic is/was not familiar with the P2106 and P1618 codes and is researching them, but in the meantime, I was wondering if anyone had any thoughts.
 
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