OBD II P0121 Code on 4.0L Jeep Wrangler: TP Sensor vs MAP Sensor Mismatch After Off-Road Driving
I'm experiencing an intermittent OBD II P0121 code on my 4.0L Jeep Wrangler, which indicates a disagreement between the Throttle Position (TP) sensor and the Manifold Absolute Pressure (MAP) sensor. The code does not appear continuously but triggers after off-road driving—such as riding through woods or rough terrain. I've already replaced both the TP and MAP sensors with no resolution. Symptoms include an erratic idle, sometimes running outside of normal range, a rough idle just before the check engine light comes on. Interestingly, once the light illuminates, the symptoms subside. Occasionally, the idle reaches nearly 3,000 RPM, and at other times, the engine will stall while idling. I'm wondering what specific repairs or diagnostics are required to fully resolve this issue. Any insights would be greatly appreciated. Dellis
It's important to verify the brand and quality of the replacement parts used. In some cases, poor connector fitment or corroded terminals can cause sensor signal issues. Additionally, a vacuum leak may contribute to the P0121 code and related symptoms—be sure to inspect all vacuum lines and connections for leaks.