2003 Dodge Durango V8 4.7L P0121 Code: Diagnosis & Solutions for TPS Voltage Issue
Hi everyone, I'm currently troubleshooting a persistent P0121 code on my 2003 Dodge Durango with the 4.7L V8 engine. Despite replacing the Throttle Position Sensor (TPS) three times, all spark plugs and coils, and performing multiple resets of the engine light — the P0121 code continues to appear repeatedly. I've visually inspected all wiring harnesses, which appear intact. However, when I measure voltage at the TPS, it consistently reads 5 volts even at idle (not during wide-open throttle). This is outside normal operating parameters and should only occur under WOT conditions. Given my situation — a single mother on a tight budget — I'm determined to keep this vehicle as it's in great condition and fits my family perfectly. What could be causing this persistent P0121 code? Are there any overlooked components or wiring issues that might explain the faulty voltage reading? Any insights, diagnostic tips, or cost-effective fixes would be greatly appreciated. Thanks in advance!
The only code present is P0121? No other symptoms like stalling, rough idle, or performance issues? Cruise control and horn functionality are normal? At the TPS location, there are three wires: 1) Orange wire — should read 5V with key on engine off (KOEO) 2) Center wire — this is the primary signal wire. With key on, expect voltage between 0.2V and 0.9V at idle. Does it increase when you open the throttle? It should rise from ~0.2–0.9V to approximately 3.5–4.5V under WOT. 3) Ground wire — should read 0 volts, confirming proper grounding. Checking these values can help isolate whether the TPS is faulty or if there's a wiring issue affecting signal transmission.