Throttle Position Sensor: Testing and Inspection

Chart C-2F - TPS Enrichment Check:

Wiring Diagram for Chart C-2F - TPS Enrichment Check:

CHART C-2F - TPS ENRICHMENT CHECK

Test Description: Step numbers refer to step numbers on diagnostic chart.

1. This step checks that the TPS will cause an ECM "Rich" command when fully depressed manually. On some cars, this will cause a low dwell (full rich). On others it will not. Code 21 should normally be set.

2. This step distinguishes between a faulty TPS or ECM harness/ECM.

Code 21 should normally be set, if engine RPM is not set above specifications.


3. This step checks for 5V. ref. at TPS. It should be about 5 volts. If loss of V. Ref were in the ECM, it should set Codes 21, 32, and 34, since this is the same 5V to MAP, BARO or VAC Sensors. Therefore, it must be an open CKT. 416.


4. This step checks for a grounded CKT 417. Normal circuit should read about 5 volts. Checking for grounded TPS output CKT 417 to Terminal "2" of ECM, or shorted CKT 417 to 452 from TPS, indicates whether fault is in wiring or ECM. A voltmeter with a 10 megohms resistance must be used for an accurate reading.