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by Bob O’Neill and Bob Lincoln
For model years before 1987, and all L-body (Omni/Horizon) models, a code 31 indicates that the purge canister solenoid circuit is open or shorted.
For models made in model-year 1987 and later which are NOT L-bodies, code 31 is thrown when the purge solenoid/ERG solenoid circuit is open or shorted.
In either case, the power limited light will not be light and the system will not enter limp mode. Code 31 is set when the ECU sees voltages near zero when the solenoid is turned on, or near 12vdc when the solenoid is turned off.
Possible reasons include:
Poor wiring or connection - Read the page ‘How to troubleshoot drivability issues’. Check the wiring and connections from the logic module to the solenoids. Clean and re-grease the connectors with dielectric grease.
Defective solenoid - The solenoids are located in the right, front fender, in a cluster of up to 4 solenoids. If a signal from the harness to the solenoid measures 12vdc when the solenoid is off the solenoid will need to be repaired or replaced. See Solenoids-101 for information about how solenoids work and how to test them..
Sensors, Switches, and Other Systems | Main Repairs Page | EEKs
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