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 MANUALSCHEVROLET1992CHEVY VAN G20, 5.7 KREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - TRANSMISSIONCOMPONENT CHECK CHARTSCODE 68, OVERDRIVE RATIO ERRORNOTES
1992 Chevrolet Chevy Van G20, 5.7 K
Code 68, Overdrive Ratio Error: Notes
1992 Chevrolet Chevy Van G20, 5.7 KSECTION Notes
The PCM/TCM monitors the difference in engine RPM and input shaft RPM. With transmission in Drive, scan tester reading should show engine speed closely matching input speed.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- Code 68 will set under the following conditions: engine speed is 200 RPM greater than input speed, 4th gear is indicated, TCC is enabled, or if all conditions are met for 2 seconds.
- This test monitors signal sent to the PCM/TCM from transmission.
- This test confirms engine RPM signal to PCM/TCM.
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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.