Chart 4 Service Engine Soon MIL Inoperative

Circuit Description

The 'SERVICE ENGINE SOON' MIL is controlled by the 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. See DTC List, 'PCM DIAGNOSTIC CODES' 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. See DTC List, '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.