1997 Dodge Ram P0123 Fault: TPS Signal Stuck at 100% - ECM Burnt Spot Confirmed
I'm working on a 1997 Dodge Ram with a 5.2L V8 engine and manual transmission. The vehicle is displaying Diagnostic Trouble Code P0123, indicating a Throttle Position Sensor (TPS) signal stuck at 100%. After thorough diagnostics: the reference voltage reads around 5V, ground connection is solid. When I disconnected the TPS sensor from its wiring harness, the middle pin (orange/blue wire) still showed 5V on the signal wire. This is normal behavior — a 5V signal should be present when the sensor is unplugged. I then cut the signal wire about three inches from the ECM plug (A23) to isolate the circuit. The result: I observed a 5V signal coming out of the ECM itself, confirming that the ECM is actively sending a constant 5V signal through the TPS wire. Upon opening the ECM unit, I found a visible burnt spot — this strongly suggests internal failure. I replaced the ECM with a new one (ordered and received today). After reassembly and power-up, the P0123 code persists, and the TPS reading remains stuck at 100%. I'm now confused about what's causing this issue. Is it possible that the ECM replacement didn
Check the TPS resistance values using a multimeter. A normal reading should be between 0.5 and 2 ohms at various throttle positions. If resistance is inconsistent or out of range, it may indicate a faulty TPS sensor or wiring issue. The presence of 5V on the signal wire when the TPS is unplugged is expected — this is part of the normal circuit behavior in most vehicles. However, if the same voltage persists when the TPS is connected and the throttle pedal is not depressed, that points to a potential fault in either the TPS sensor or its wiring circuit.