P0503

[Airfrm]

I have a 2008 2500 with the 6.7L. A few days ago I was pulling a trailer uphill and as I accelerated, I lost all power and the transmission would not downshift and I got a check engine light. After I got back on flat road, I was able to regain my power. After while, the check engine light went out, but I was able to verify it was a P0503. So I am wondering if anyone else has had this issue, and is it just the vehicle speed sensor, or is this potentially a transmission failure in the making?

 

[Tom Davis]

Hope this helps.

Here's a site to help with codes and what they mean.

Diagnostic Trouble Code (DTC) Definition, Causes and Diagnosis

Diagnostic Trouble Code (DTC) Definition, Causes and Diagnosis

www.dtcdecode.com

RAM DTC P0503​

Make: RAM
Code: P0503
Definition: Vehicle Speed Sensor 1 Erratic
Description: The vehicle speed sensor rationality is a continuous test that monitors the vehicle speed sensor for lack of activity. The Powertrain Control Module (PCM) receives this information from the Anti-Lock Brake System over the CAN C bus. The CAN C bus is a high speed communication bus that allows real time control capability between various controllers. The rationality test will not run if a limp-in exists for MAP, Throttle Position, Crankshaft Sensor, Camshaft Sensor, and Engine Coolant Temperature, if the brake is applied or any Brake Switch codes are set. If vehicle speed signal is below a minimum threshold for a calibrated period of time after the vehicle has been operating within the modeled parameters that would indicate it is being driven, a failure will be indicated.

Cause:

• ACTIVE BUS OR COMMUNICATION DTCS
• TIRE CIRCUMFERENCE
• POWERTRAIN CONTROL MODULE (PCM)