P0121

Wiring Diagram:

The PCM has an internal table that looks at MAP sensor values with respect to TP sensor values. If the throttle position sensor indicates the engine is near wide open throttle but the MAP sensor reading indicates the high vacuum reading (decel or idle), this DTC will set.

DTC PARAMETERS

DTC P0121 will set if the TP sensor vs MAP sensor relationship is not consistent with normal engine operation (low MAP reading and high TP reading) when:

^ Engine is running.
^ MAP is greater than 54.6 kPa.
^ TP sensor change is less than 2%
^ No TP sensor or MAP sensor DTCs have been set.

NOTE: The TP signal range is continuously checked when the above conditions have been met.

DIAGNOSTIC AIDS

DTC P0121 indicates that either the TP sensor or MAP sensor is skewed outside its normal operating range.

Check TP sensor and MAP sensor connectors for corrosion.

Check PCM connector for corrosion.

Move throttle and check TP sensor voltage readings on Scan tool. If throttle moves without a change in TP sensor voltage the TP sensor return spring may be sticking. If this condition occurs, replace TP sensor.

At a closed throttle position, the output of the TP sensor is low (approximately 0.4 volts). As the throttle plate opens, the output increases so that, at wide-open throttle, the output voltage should be approximately 4.9 volts.

When attempting to diagnose an intermittent problem, use the Scan tool to review malfunction history information. This data can be used to duplicate a problem.

Check the tightness of the female terminal grip with a spare male terminal.