2007 Commander XK Factory Service Manual 8 - ELECTRICAL

DIAGNOSIS AND TESTING

B2336-HORN CONTROL CIRCUIT LOW - FCM





For a complete wiring diagram Refer to Section 8W.


  • When Monitored:

    Continuously.

  • Set Condition:

    If the Front Control Module (FCM) senses either excessively low or no voltage on the (X4) Horn Relay Control circuit.


Possible Causes
  
(A43) FUSED B(+) CIRCUIT SHORTED TO GROUND
  
(X4) HORN RELAY CONTROL CIRCUIT SHORTED TO GROUND
  
(A1) / (A913) CIRCUIT OPEN TO HORN FUSE
  
(A43) FUSED B(+) CIRCUIT OPEN
  
(X4) HORN RELAY CONTROL CIRCUIT OPEN
  
HORN FUSE
  
HORN RELAY
  
INTEGRATED POWER MODULE (IPM)
  
FRONT CONTROL MODULE (FCM)
  



Diagnostic Test

1. TEST FOR INTERMITTENT CONDITION

Turn the ignition on.
With the scan tool, record and erase DTCs.
Operate the Horn Switch several times.
Cycle the ignition from on to off three times and leave on.
With the scan tool, read DTCs.

Does the scan tool display: B2336 HORN CONTROL CIRCUIT LOW?

Yes


No

2. CHECK THE HORN FUSE



Turn the ignition off.
Remove and inspect the Horn fuse.

Is the Horn Fuse open?

Yes


No

3. CHECK FOR A SHORTED HORN RELAY



Install a known good relay in place of the Horn Relay.
Replace the Horn fuse.
Turn the ignition on.
With the scan tool, record and erase DTCs.
Operate the Horn Switch several times.
Cycle the ignition from on to off three times and leave on.
With the scan tool, read DTCs.

Does the scan tool display: B2336 HORN CONTROL CIRCUIT LOW?

Yes


No

4. CHECK THE (A43) FUSED B(+) CIRCUIT FOR A SHORT TO GROUND



Turn the ignition off.
Remove the Horn Relay.
Remove the Horn Fuse.
Measure the resistance of the (A43) Fused B(+) circuit between ground and Cavity 86 of the Horn Relay connector in the Integrated Power Module (IPM).
Measure the resistance of the (A43) Fused B(+) circuit between ground and Cavity 30 of the Horn Relay connector in the Integrated Power Module (IPM).

Is the resistance below 10k ohms?

Yes


No

5. CHECK THE (X4) HORN RELAY CONTROL CIRCUIT FOR A SHORT TO GROUND



Remove the Front Control Module (FCM) in accordance with the Service Information.
Measure the resistance of the (X4) Horn Relay Control circuit between ground and Cavity 85 of the Horn Relay connector in the Integrated Power Module (IPM).

Is the resistance below 10k ohms?

Yes


No

6. CHECK FOR A SHORTED INTEGRATED POWER MODULE (IPM)



Install the original Horn Relay.
Replace the Horn fuse.
Turn the ignition on.
With the scan tool, record and erase DTCs.
Operate the Horn Switch several times.
Cycle the ignition from on to off three times and leave on.
With the scan tool, read DTCs.

Does the scan tool display: B2336 HORN CONTROL CIRCUIT LOW?

Yes


No

7. CHECK FOR POWER TO THE HORN FUSE



Turn the ignition on.
Using a 12-volt test light connected to ground, check for power to the Horn Fuse.

Does the test light illuminate brightly?

Yes


No

8. CHECK FOR AN OPEN HORN RELAY



Turn the ignition off.
Install a known good relay in place of the Horn Relay.
Turn the ignition on.
With the scan tool, record and erase DTCs.
Operate the Horn Switch several times.
Cycle the ignition from on to off three times and leave on.
With the scan tool, read DTCs.

Does the scan tool display: B2336 HORN CONTROL CIRCUIT LOW?

Yes


No

9. CHECK THE (A43) FUSED B(+) CIRCUIT FOR AN OPEN



Turn the ignition off.
Remove the Horn Relay.
Remove the Horn Fuse.
Measure the resistance of the (A43) Fused B(+) circuit between the Horn Fuse (output cavity) and Cavity 86 of the Horn Relay connector in the Integrated Power Module (IPM).
Measure the resistance of the (A43) Fused B(+) circuit between the Horn Fuse (output cavity) and Cavity 30 of the Horn Relay connector in the Integrated Power Module (IPM).

Is the resistance below 5.0 ohms?

Yes


No

10. CHECK THE (X4) HORN RELAY CONTROL CIRCUIT FOR AN OPEN



Remove the Front Control Module (FCM) in accordance with the Service Information.
Measure the resistance of the (X4) Horn Relay Control circuit between Cavity 85 of the Horn Relay connector in the Integrated Power Module (IPM) and Cavity 47 of the FCM 49-Way connector.

Is the resistance below 5.0 ohms?

Yes


No

B2337-HORN CONTROL CIRCUIT HIGH - FCM





For a complete wiring diagram Refer to Section 8W.


  • When Monitored:

    Continuously.

  • Set Condition:

    If the Front Control Module (FCM) senses excessive voltage on the (X4) Horn Relay Control circuit.


Possible Causes
  
(X4) HORN RELAY CONTROL CIRCUIT SHORTED TO VOLTAGE
  
HORN RELAY
  
INTEGRATED POWER MODULE (IPM)
  
FRONT CONTROL MODULE (FCM)
  



Diagnostic Test

1. TEST FOR INTERMITTENT CONDITION

Turn the ignition on.
With the scan tool, record and erase DTCs.
Operate the Horn Switch several times.
Cycle the ignition from on to off three times and leave on.
With the scan tool, read DTCs.

Does the scan tool display: B2337 HORN CONTROL CIRCUIT HIGH?

Yes


No

2. CHECK FOR A SHORTED HORN RELAY



Turn the ignition off.
Install a known good relay in place of the Horn Relay.
Turn the ignition on.
With the scan tool erase DTCs.
Operate the Horn Switch several times.
Cycle the ignition from on to off three times and leave on.
With the scan tool, read DTCs.

Does the scan tool display: B2337 HORN CONTROL CIRCUIT HIGH?

Yes


No

3. CHECK THE (X4) HORN RELAY CONTROL CIRCUIT FOR A SHORT TO VOLTAGE



Turn the ignition off.
Remove the Horn Relay.
Remove the Front Control Module (FCM) in accordance with the Service Information.
Turn the ignition on.
Measure the voltage of the (X4) Horn Relay Control circuit.

Is the voltage above 0.2 volts?

Yes


No

B2339-HORN SWITCH STUCK - SCCM





For a complete wiring diagram Refer to Section 8W.

Theory of Operation


The Horn Switch connects to the Steering Column Control Module (SCCM) via a serial sub-bus called the LIN bus. The SCCM monitors the Horn Switch status. When the switch status changes (switch is pressed or released), the SCCM processes the request and broadcasts it on the CAN B Bus where it is read and processed by the Front Control Module (FCM).


  • When Monitored:

    Continuously.

  • Set Condition:

    If the Steering Column Control Module (SCCM) senses that the Horn Switch is in the Set position for more than 50 seconds.


Possible Causes
  
(X3) HORN SWITCH SIGNAL CIRCUIT SHORTED TO (X903) HORN SWITCH RETURN CIRCUIT
  
(X3) HORN SWITCH SIGNAL CIRCUIT SHORTED TO GROUND
  
HORN SWITCH
  
STEERING COLUMN CONTROL MODULE (SCCM)
  



Diagnostic Test

1. TEST FOR INTERMITTENT CONDITION

NOTE: If DTC P0562 BATTERY VOLTAGE LOW or DTC P0563 BATTERY VOLTAGE HIGH is active along with this DTC, diagnose and repair the battery voltage related DTC first.


Turn the ignition on.
With the Scan Tool, select View DTCs in the Steering Column Control Module (SCCM).

Does the scan tool display DTC B2339 HORN SWITCH STUCK active?

Yes


No

2. TEST THE HORN SWITCH

Turn the ignition off.
Remove the Driver Airbag in accordance with the Service information.
Disconnect the Horn Switch connector.
Measure the resistance between the (X3) Horn Switch Signal circuit and the (X903) Horn Switch Return circuit in the Horn Switch while pressing and releasing the switch several times.

Does the ohmmeter reading indicate continuity when the switch is pressed and no continuity when the switch is released?

Yes


No

3. CHECK THE (X3) HORN SWITCH SIGNAL CIRCUIT FOR A SHORT TO THE (X903) HORN SWITCH RETURN CIRCUIT



Disconnect the Steering Control Module C3 connector.
Measure the resistance between the (X3) Horn Switch Signal circuit and the (X903) Horn Switch Return circuit in the Horn Switch Connector.

Is the resistance below 10k ohms?

Yes


No

4. CHECK THE (X3) HORN SWITCH SIGNAL CIRCUIT FOR A SHORT TO GROUND



Measure the resistance between ground and the (X3) Horn Switch Signal circuit in the Horn Switch Connector.

Is the resistance below 10k ohms?

Yes


No