DTC 22

Fig. 18 Throttle position sensor wiring circuit:

If this code is not displayed during the third pass of diagnostic codes, the problem is an intermittent failure. To help isolate the problem, manipulate related wiring while observing parameter .0.1. If the failure is induced,the reading will jump from its normal value to an open reading of (-)10 to - 6° at part throttle.
Code 22 indicates that voltage signal from throttle position sensor is too low. The ECM operates internally on 5 volts. The throttle position sensor operation is such that 5 volts are applied to pin C through the resistor and to ground in the ECM through pin B. Pin A is the throttle position sensor signal line which provides a variable voltage depending on throttle position to the ECM. A low voltage reading may be caused by the following:
a. Defective sensor.
b. No 5 volt input from ECM to sensor.
c. Defective or improperly connected wiring.
d. ECM cannot process signal.

To diagnose a Code 22, proceed as follows:
1. Turn ignition on, enter diagnostics and display parameter .0.1. At part throttle, value of parameter .0.1 should be (-)10° to (-)6°.
2. Disconnect TPS connector and connect a jumper wire between pins A and C.
3. If value of parameter .0.1 is 87 to 90, check for a faulty TPS or loose sensor terminal connections. Repair or replace as necessary.
4. If value of parameter .0.1 is 86 or less, remove jumper wire and connect a voltmeter between pin C and ground.
5. If no voltage is recorded, check circuit 474 for an open and repair as necessary.
6. If voltmeter reads 5 volts, measure voltage between circuits 474 and 417.
7. If voltage is 5 volts, check circuit 417 for short to ground or to circuit 476. If wiring is satisfactory, fault is in ECM or ECM connector.
8. If voltmeter reads 0 volts, connect a jumper wire between blue ECM connector pin 5 and red connector pin 11.
9. If value of parameter .0.1 is 87 to 90, check circuit 417 for an open and repair as necessary.
10. If value of parameter .0.1 is 86 or less, fault is in ECM or ECM connector.