Chart 4 Service Engine Soon MIL Inoperative

Chart Number 4:

Service Engine Soon Circuit:

CIRCUIT DESCRIPTION:
The Malfunction Indicator Lamp (MIL) (Service Engine Soon) 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.

MALFUNCTION INDICATOR LAMP ON
1. MALFUNCTION: When certain PCM codes are current. Refer to Diagnostic Trouble Code Description, PCM Diagnostic Troulbe Codes for those codes that turn "ON" the 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 Diagnostic Trouble Code Description, "PCM DIAGNOSTIC CODES" for those codes that DO NOT turn "ON" the "SERVICE ENGINE SOON" MIL.

NOTES ON FAULT TREE
1. Checking the third digit of PD16 to determine if the PCM is receiving the correct input voltage expected. With the "SERVICE ENGINE SOON" MIL "ON," the PCM expects to see "0" volt on pin "3F5." If it is, the third digit of PD16 will be "0." If it sees more than "0" volt, the third digit of PD16 will be "1."

2. Checking if correct voltage is being received at the PCM and it is not processing it correctly.

3. Checking CKT 419 for an open.

4. Checking for voltage to the high side of the MIL bulb.