Experiencing a P0123 OBD2 code on your 2000 Dodge Durango can be frustrating. This code typically indicates a high input signal from the Throttle Position Sensor (TPS), suggesting a potential issue with the sensor or its circuit. Like many, initial troubleshooting steps might lead you down incorrect paths. In my case, chasing this code involved replacing components that ultimately weren’t the root cause.
Initially, suspecting a faulty Powertrain Control Module (PCM) or a clock spring issue – based on suggestions from online forums – I replaced both. Unfortunately, these replacements didn’t resolve the persistent P0123 code. The breakthrough came from a moment of diagnostic frustration. While monitoring the TPS signal wire voltage with a digital voltmeter, which was reading an abnormally high 5.8V, I began methodically pulling fuses and relays in the underhood fuse block. Surprisingly, removing the stop lamp fuse caused the voltage to drop to a normal 4.6V. Starting the Durango after this fuse removal resulted in the engine running smoothly, seemingly fixing the P0123 issue.
However, the correlation between the stop lamps and the TPS was unclear and logically unrelated. Further investigation into the stop lamp circuit wiring led to the discovery of coolant leaking from the large C200 connector, located where the wiring harness passes through the firewall near the driver’s side floorboard. This coolant leak explained puddles previously observed in the shop. The source of the leak was traced back to the auxiliary coolant pump, situated under the hood by the firewall on the passenger side. This leaking pump had been forcing coolant through the wiring harness, reaching the C200 connector inside the vehicle.
The coolant contamination within the C200 connector was the culprit behind the high TPS voltage and the P0123 code. Cleaning out the C200 connector with compressed air and reconnecting it rectified the issue. The TPS voltage returned to the correct 4.6V, and the 2000 Dodge Durango ran perfectly.
The key takeaway from this experience is to address coolant leaks promptly, especially those originating from the auxiliary coolant pump in 2000 Dodge Durango models. Ignoring such leaks can lead to unforeseen electrical problems, such as a P0123 code triggered by coolant intrusion into wiring connectors, creating a far more complex diagnostic challenge than initially anticipated. Always consider seemingly unrelated systems when troubleshooting electrical issues, and don’t overlook the possibility of fluid leaks impacting electrical components.
