Rick's Free Auto Repair Advice

P1494 EVAP Leak Detection Pump

Fix code P1494 EVAP Leak Detection Pump Switch or Mechanical Fault

If you have a P1494 EVAP Leak Detection Pump Switch or Mechanical Fault trouble code, this post will help you understand what it is and how to fix it.

To diagnose this problem, follow this procedure:

Turn the key to the ON position. Check for battery voltage on the power supply wire (pink/grey)at the 3-way connector located on the Leak Detection Pump. If you detect battery voltage on more than 1 wire, the wire harness is shorted and must be repaired before proceeding with other tests.

If you find battery voltage on the power supply wire, reconnect the connector. Use your computer-safe test light to backprobe the the LDP “sense circuit” (purple/white) at the connector. You should see power on this wire at key ON. Use a jumper wire to quickly backprobe the purple/blue (solenoid) wire and touch the other end to ground. The test light should go out when the solenoid operates. When you remove the ground wire, the light should go on again. If you don’t get this result, either you have a short to ground in the wiring harness “sense” circuit, or the LDP is bad.

Next, disconnect the connector at the PCM and the LDP and check the wiring harness for a short to ground on the sense circuit.

If all the electrical repairs check out, the problem is a vacuum leak.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat


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