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 MANUALSPONTIAC1987BONNEVILLE SEREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEM5.0L FEEDBACK CARBURETOR "C" CHARTSCHART C2F - TPS ENRICHMENT CHECK
1987 Pontiac Bonneville SE
Chart C2F - TPS Enrichment Check
1987 Pontiac Bonneville SESECTION Chart C2F - TPS Enrichment Check
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- This test 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). Code 21 should normally be set.
- This step distinguishes between a faulty TPS, ECM or ECM harness. Code 21 should normally be set if engine RPM is not set above specifications.
- This tests for 5-volt reference signal at TPS. It should be about 5 volts. If loss of voltage reference were in ECM, it should set codes 21, 32 and 34, since it is the same 5 volt reference to MAP, BARO or VAC sensors. Therefore it must be an open in wiring.
- This tests for a grounded circuit. Normal circuit should read about 5 volts. Checking for grounded TPS output to terminal "2" of ECM, or short in wiring to terminals "2" and "22" from TPS, indicates whether fault is in wiring or ECM. A voltmeter with a 10 megaohm resistance must be used for an accurate reading.
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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.