Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET1986C 10 P/U 2WD V8-350 5.7LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTHROTTLE POSITION SENSORTESTING AND INSPECTION
1986 Chevrolet C 10 P/U 2WD V8-350 5.7L
Throttle Position Sensor: Testing and Inspection
1986 Chevrolet C 10 P/U 2WD V8-350 5.7LSECTION 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:
1. This step checks that the TPS will cause an ECM "Rich" command when fully depressed manually. On some vehicles, 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 VAC Sensor. Therefore, it must be an open in the wire.
4. This step checks for a grounded circuit. Normal circuit should read about 5 volts. Checking for grounded TPS output to Terminal "2" of ECM, or short in CKT 417 and 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.
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.