Code 89
PURGE VALVE DRIVE CIRCUIT - DTC 89
The ECM looks for the purge valve drive circuit voltage to the outside the expected range when the valve is switched ON and OFF.
The ECM drives the purge valve by grounding the purge valve solenoid coil. The drive signal (pulse width modulated) is a square wave that is mapped in the ECM to provide optimum purge rates. When purge is enabled, the frequency of the drive signal is constant, but the dwell ("valve open" time) changes with engine load and speed. If the oxygen sensor detects excess air in the exhaust, the ECM closes the purge valve for up to 20 minutes. allowing the canister to collect more vapor.
Purge Valve Signal:
The ECM monitors the purge valve drive signal and checks that when the valve is closed, the drive signal is close to ground and when the valve is opened, the signal is near battery voltage. The exact voltage levels vary depending upon battery voltage.
The ECM will flag DTC 89 if the drive circuit voltage is greater than approximately 2.5 volts when the purge valve is driven closed, or if the drive circuit voltage is less than approximately 10.5 volts when the purge valve is driven open.
Conditions Required For DTC 89 Flagging
Purge drive signal - ON (valve closed).
Drive circuit voltage - Greater than 2.5 volts (approximate).
Purge drive - OFF (valve open).
Drive circuit voltage - Less than 10.5 volts (approximate).
Limp Home Default
None
Possible Faults
- Low battery voltage.
- Poor ECM power feed or ground connections.
- Open or short circuit wiring in the purge valve drive circuit.
- Open circuit wiring in the purge valve power supply circuit.
- Defective purge valve.
Diagnostic Notes
1. The purge drive signal can be monitored with an oscilloscope.
2. The purge valve coil resistance should be approximately 42 ohms.
3. Intermittent power loss will flag DTC 89. Check the security of the connections to the left and right bulkhead power studs (passenger side - XJ6 Sedan Range vehicles; engine side - XJS Range vehicles).
4. 1990 - 92 XJ6 Sedan Range vehicles - Intermittent faults can be caused by loose terminal pins in connector LI18 (yellow PM4) located below the air cleaner housing. Remove the female pins from the connector block and inspect for a loose condition. The contact tangs must bend toward the inside of the female terminal.
Purge Valve Test
To test for an inoperative or sticking purge valve: Disconnect the purge hose at the intake manifold adapter.
- Switch ignition ON; do not start the engine.
- Apply vacuum to purge hose; vacuum should hold. If the vacuum does not hold, the purge valve is stuck and should be replaced.
- Switch ignition OFF; vacuum should release after a few seconds. If the vacuum does not release, the purge valve is stuck and should be repaced.
Circuit Diagram
Circuit Diagram:
�W�Flow Chart - DTC 89:
