Chart 5 Service Engine Soon MIL On, No PCM Codes Set

Chart Number 5:

Service Engine Soon Circuit:

CIRCUIT DESCRIPTION
The "SERVICE ENGINE SOON" Malfunction Indicator Lamp (MIL) is controlled by the Powertrain Control Module (PCM) through CKT 419 and indicates that the PCM has detected a problem that affects vehicle emissions, may cause powertrain damage or severely impacts driveability.

"SERVICE ENGINE SOON" MIL ON
1. MALFUNCTION: When certain PCM codes are current. Refer to "PCM Diagnostic Code Description" for those codes that turn "ON" the "SERVICE ENGINE SOON" MIL.

2. DIAGNOSTIC MODE: After the indicator and segment check, the telltale should remain "ON."

"SERVICE ENGINE SOON" MIL OFF
1. Key "ON," engine not running.

2. ENGINE RUNNING: No PCM codes current. The telltale can be "OFF" with PCM codes stored. Refer to "PCM Diagnostic Code Description" for those codes that DO NOT turn "ON" the "SERVICE ENGINE SOON" MIL.

NOTES ON FAULT TREE
1. At key "ON," the "SERVICE ENGINE SOON" MIL should be "OFF." Checking if fault is present.

2. Checking for a code which may have turned "ON" the MIL.

3. If the "SERVICE ENGINE SOON" MIL goes "OFF" when PCM connector "3E/3F" is disconnected, replace the PCM. If the MIL stays "ON," repair CKT 419 for a short to ground.