Test Procedure
WARNING: This page does not describe the selected car, but rather 30 other vehicles, including the 2004 Mercury Sable, 2004 Mercury Mountaineer, 2004 Mercury Monterey, 2004 Mercury Marauder, and 2004 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.
- NB1 MALFUNCTION INDICATOR LAMP ALWAYS ON (NO DTCS PRESENT)
Does the vehicle start?
Yes No GO to NB2. Concern is elsewhere. RETURN to SYMPTOM CHARTS - CNG, FLEX-FUEL & GASOLINE for further direction. - NB2 CHECK THE MIL CIRCUIT FOR A SHORT TO GROUND IN THE HARNESS
- PCM connector disconnected.
- Measure the resistance between:
( + )PCM Connector, Harness Side ( - )Vehicle battery MIL - Pin 2 Negative terminal Is the resistance greater than 10K ohms?
Yes No INSTALL a new PCM.
Refer to FLASH ELECTRICALLY ERASEABLE PROGRAMMABLE READ ONLY MEMORY - FLASH EEPROM .REPAIR short circuit to GND. - NB3 MALFUNCTION INDICATOR LAMP (MIL) NEVER ON
Does the vehicle start?
Yes No GO to NB4. Concern is elsewhere. RETURN to SYMPTOM CHARTS - CNG, FLEX-FUEL & GASOLINE for further direction. - NB4 MIL HARNESS CHECK
- PCM connector disconnected.
- Key ON Engine OFF.
- Connect a 5 amp fused jumper wire between the following:
Point A PCM Connector, Harness Side Point B MIL - Pin 2 Ground - REMOVE jumper wire(s)
Did the MIL Illuminate when grounded?
Yes No KEY OFF. INSTALL a new PCM. KEY OFF
GO to NB5. - NB5 CHECK THE VOLTAGE ON THE B+ CIRCUIT
- PCM disconnected.
- IC connector disconnected.
- Key ON Engine OFF.
- Measure the voltage between:
( + )IC Connector, Harness Side ( - )Vehicle battery B+ Negative terminal Is the voltage greater than 10.5 V?
Yes No KEY OFF
GO to NB6.KEY OFF. REPAIR open circuit. - NB6 CHECK FOR AN OPEN MIL CIRCUIT BETWEEN THE PCM AND INSTRUMENT CLUSTER
- PCM disconnected.
- IC connector disconnected.
- Measure the resistance between:
( + )PCM Connector, Harness Side ( - )IC Connector, Harness Side MIL - Pin 2 MIL Is the resistance less than 5 ohms?
Yes No Refer to the appropriate INFORMATION, GAUGES & WARNING DEVICES INSTRUMENT CLUSTER article for instrument cluster diagnostics
If OK, REPLACE the PCM.
Refer to FLASH ELECTRICALLY ERASEABLE PROGRAMMABLE READ ONLY MEMORY - FLASH EEPROM
VERIFY the repair by turning the key to the ON position.REPAIR open circuit
VERIFY the repair by turning the key to the ON position.