Engine Control Module - ECM

Diagnostic Trouble Code 22:

TP Sensor Circuit:

CIRCUIT DESCRIPTION
The Throttle Position (TP) sensor provides a voltage signal which changes relative to the throttle blade. Signal voltage will vary from about 0.5 volt at idle to about 4.0 volts at Wide Open Throttle (WOT).

The TP signal is one of the most important inputs used by the ECM for fuel control and for most of the ECM control outputs.

On non-adjustable TP switches, each time voltage drops below 1.25 volts and stops, the ECM assumes this value is 0 throttle angle and measures percent throttle from this point on.

DTC 22 WILL SET WHEN
^ Engine running.
^ TP signal voltage is less than 0.2 volt for two seconds.

ACTION TAKEN (ECM WILL DEFAULT TO)
The Malfunction Indicator Lamp (MIL) will illuminate.

DTC 22 WILL CLEAR WHEN
Conditions for fault are no longer present and Tech 1 "Clear DTCs" function is used or 50 ignition switch keycycles have passed with no further faults or ignition switch is turned "OFF" and battery feed voltage is removed for 10 seconds.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. This step checks to see if DTC 22 is the result of a hard failure or an intermittent condition.

2. Simulates DTC 21: (high voltage) - If the ECM recognizes the high signal voltage, the ECM and wiring are OK.

3. The ECM recognizes the voltage as over 4 volts, indicating that the TP signal circuit and the ECM are OK.

4. This simulates a high signal voltage to check for an open in the TP signal circuit.

5. If the 5 volt reference circuit is shorted to ground, there may also be a stored DTC 34.

DIAGNOSTIC AIDS
A scan tool reads throttle position in volts. Should read about 0.45 to 0.85 volt with throttle closed and ignition "ON" or at idle. Voltage should increase at a steady rate as throttle is moved toward WOT.

An open or short to ground in the 5 volt reference circuit or the TP signal circuit will result in a DTC 22.

Refer to Diagnosis By Symptom / Intermittents - Intermittent Malfunctions

Scan TP signal while depressing accelerator pedal with engine stopped and ignition "ON." Display should vary from below 1.25 volts (1250 mV) when throttle was closed to over 4.5 volts (4500 mV) when throttle is held at WOT position.