P0221

Schematic:

The throttle actuator control (TAC) module contains two throttle position (TP) sensors with a common 5 volt supply, a common ground, and two independent signal circuits that vary resistance according to changes in throttle plate position. The ECM measures the signal voltage from each TP sensor, which is a reduced value of the ECM 5 volt reference. As the throttle plate opens from 0% throttle to wide open throttle, the voltage on the TP sensor 1 signal increases from 0.50 volts to 4.25 (+/-0.1) volts, while the voltage on the TP sensor 2 signal decreases from 4.45 volts to 0.70 (+/-0.1) volts. DTC P0221 sets when the TP sensor 2 and TP sensor 1 signals are out of correlation, and TP sensor 2 signal indicates too large of a difference in throttle angle based on the mass air flow (MAF) sensor signal.

DTC PARAMETERS
DTC P0221 will set if TP sensor 2 signal voltage is not rational when:
^ TP sensor 2 and TP sensor 1 signal voltages are out of correlation by greater than 6.25% for longer than 140 ms, while TP sensor 2 signal is out of correlation from the MAF sensor signal by greater than 9% for longer than 400 ms.
^ Engine speed is greater than 480 rpm
^ Main relay voltage is greater than 8.0 volts
^ No other TP sensor 2 DTCs have been set

DTC P0221 diagnostic runs continuously once the above conditions have been met.

P0221 is a type B DTC.

DIAGNOSTIC AIDS

IMPORTANT:
^ If a TP sensor 1 or TP sensor 2 low or high voltage circuit fault is also set, diagnose that DTC first.
^ If DTC P0121 is also set, resistance may exist in the five volt Ref-B circuit 486 or reference return circuit 2752. Check for corrosion and for loose or spread terminals.

A skewed TP sensor 2 can set this DTC. Monitor the voltage range of the sensor using THROTTLE ACTUATOR CONTROL in the SPECIAL FUNCTIONS of the Scan tool, which will command the throttle actuator control module to move the throttle plate. The approximate (+/-0.1) TP SENSOR 1 vs TP SENSOR 2 voltages should be:

TP Sensor 1 TP Sensor 2
0% / 0.50 v = 4.45 volts
7% / 0.82 v = 4.17 volts
25% / 1.45 v = 3.55 volts
50% / 2.45 v = 2.55 volts
75% / 3.35 v = 1.65 volts
100% / 4.25 to 4.62 v = 0.70 to 0.16 volts

NOTE: TP ANGLE on Scan tool is based off of TP sensor 1 only.