Ford Mustang (1999-2004) Service Manual: Pinpoint Test P: No Communication With The Restraints Control Module

Normal Operation

The RCM communicates with the scan tool using ISO 9141 communication mode through the data link connector (DLC).

Possible Causes

A no communication condition can be caused by:

  • damage to circuit 70 (LB/WH).
  • a damaged DLC.
  • a damaged scan tool.
  • an RCM internal concern.

PINPOINT TEST P: NO COMMUNICATION WITH THE RESTRAINTS CONTROL MODULE

Test Step Result / Action to Take
P1 CHECK THE RCM CONNECTOR C2041 AND CONNECTOR PIN 5 FOR DAMAGE Yes

GO to P2 .

No

REPAIR RCM C2041 or RCM C2041 pin 5 as necessary.

REACTIVATE the system.
WARNING: If the supplemental restraint system (SRS) is being serviced, the system must be deactivated and restraint system diagnostic tools must be installed. Refer to Air Bag Supplemental Restraint System (SRS) in this section.

The air bag restraint system diagnostic tools must be removed and the air bag modules reconnected when the system is reactivated to avoid non-deployment in a collision, resulting in possible personal injury.

NOTE: Diagnostics or repairs are not to be performed on a seat equipped with a seat side air bag with the seat in the vehicle. Prior to attempting to diagnose or repair a seat concern when equipped with a seat side air bag, the seat must be removed from the vehicle and the restraint system diagnostic tools must be installed in the seat side air bag electrical connectors. The restraint system diagnostic tools must be removed prior to operating the vehicle over the road.

NOTE: After diagnosing or repairing an SRS, the restraint system diagnostic tools must be removed before operating the vehicle over the road.

NOTE: After diagnosing or repairing a seat system, the restraint system diagnostic tools must be removed before operating the vehicle over the road.

NOTE: The SRS must be fully operational and free of faults before releasing the vehicle to the customer.

  • Key in OFF position.
  • Deactivate the system. Refer to Air Bag Supplemental Restraint System (SRS) in the Diagnosis and Testing portion of this section.
  • Key in OFF position.
  • Disconnect: RCM C2041.
  • Inspect RCM C2041, harness side and RCM C2041, component side, pin 5 for damage.
  • Are RCM C2041 and RCM C2041 pin 5 OK?
P2 CHECK THE DLC CONNECTOR C251 AND CONNECTOR PIN 7 FOR DAMAGE Yes

GO to P3 .

No

REPAIR DLC C251 or DLC C251 pin 7 as necessary.

RETEST the communication to RCM.

RECONNECT the system.

REACTIVATE the system. PROVE OUT the system.

REFER to Air Bag Supplemental Restraint System (SRS) in this section.
  • Inspect DLC C251 and DLC C251 pin 7 for damage.
  • Are DLC C251 and DLC C251 pin 7 OK?
P3 CHECK CIRCUIT 70 (LB/WH) FOR SHORT TO BATTERY Yes

REPAIR the battery short. RETEST the communication to RCM.

RECONNECT the system.

REACTIVATE the system. PROVE OUT the system.

REFER to Air Bag Supplemental Restraint System (SRS) in this section.

No

GO to P4
  • Measure the voltage to ground at DLC C251 pin 7, circuit 70 (LB/WH).

  • Can any voltage be measured?
P4 CHECK CIRCUIT 70 (LB/WH) FOR SHORT TO GROUND Yes

REPAIR the circuit.

RETEST the communication to RCM.

RECONNECT the system.

REACTIVATE the system. PROVE OUT the system.

REFER to Air Bag Supplemental Restraint System (SRS) in this section.

No

GO to P5
  • Measure the resistance to ground at DLC C251 pin 7, circuit 70 (LB/WH).

  • Is the resistance less than 10,000 ohms?
P5 CHECK CIRCUIT 70 (LB/WH) FOR AN OPEN Yes

INSTALL a new RCM. RETEST the communication to RCM.

RECONNECT the system.

REACTIVATE the system. PROVE OUT the system.

REFER to Air Bag Supplemental Restraint System (SRS) in this section.

No

REPAIR the circuit.

RETEST the communication to RCM.

RECONNECT the system.

REACTIVATE the system. PROVE OUT the system.

REFER to Air Bag Supplemental Restraint System (SRS) in this section.
  • Measure the resistance between RCM C2041 pin 5, circuit 70 (LB/WH), harness side and DLC C251 pin 7, circuit 70 (LB/WH), harness side

  • Is the resistance less than 5 ohms?
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