Test A (Code 39) Compressor Relay Circuit
- Horn circuit and air suspension circuit use same type of relay. Depress horn pad to ensure horn is working. Remove horn relay, located in fuse/relay box directly behind battery, and install in place of compressor relay. Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS. If Code 39 is displayed, install relays in original position and go to next step. If Code 39 is not displayed, install horn relay in original position. Replace compressor relay. Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS.
- Turn air suspension switch to OFF position. Disconnect control module connectors. Remove compressor relay from fuse/relay box located in engine compartment, behind battery. Turn air suspension switch to ON position. Using a voltmeter, measure voltage between pins No. 23 and No. 6 on harness side of module connectors. See Fig 1 .
- If zero volts are indicated, replace control module. Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS. If battery voltage is indicated, repair short circuit to battery in circuit No. 420 (Dark Blue/Yellow wire). Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS.