Dodge Ram Truck 1500-2500-3500. Manual — part 286

MIC MESSAGES NOT RECEIVED (FCM)

For a complete wiring diagram Refer to Section 8W.

•

When Monitored:
With the ignition on.

•

Set Condition:
The FCM does not receive any messages from the MIC for at least 5 seconds.

Possible Causes

(D25) PCI BUS CIRCUIT OPEN

INSTRUMENT CLUSTER POWER AND GROUND

FRONT CONTROL MODULE

Diagnostic Test

1.

ATTEMPT TO COMMUNICATE WITH THE INSTRUMENT CLUSTER (MIC)

Turn the ignition on.

With the DRB, enter Body then Electro/Mech Cluster.

Was the DRB able to I/D or communicate with the Instrument Cluster (MIC)?

Yes

>> Go To 2

No

>> Refer to the table of contents and perform the related symptom.

Perform BODY VERIFICATION TEST - VER 1. (Refer to BODY VERIFICATION TEST - VER 1.)

2.

FRONT CONTROL MODULE

With the DRB, erase DTC’s.

Turn the ignition on and wait approximately 1 minute.

With the DRB, read DTC’s.

Did this DTC reset?

Yes

>> Replace the Front Control Module in accordance with the service information.

Perform BODY VERIFICATION TEST - VER 1. (Refer to BODY VERIFICATION TEST - VER 1.)

No

>> The condition that set this DTC is no longer present. Using the wiring diagram/schematic as a guide,

inspect the wiring for chafed, pierced, pinched, and partially broken wires and the wiring harness con-
nectors for broken, bent, pushed out, and corroded terminals.

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ELECTRONIC CONTROL MODULES - ELECTRICAL DIAGNOSTICS

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PCI BUS INTERNAL - LOOPBACK FAILURE (FCM)

For a complete wiring diagram Refer to Section 8W.

•

When Monitored:
Continuously

•

Set Condition:
When the loopback test has failed.

Possible Causes

FRONT CONTROL MODULE

Diagnostic Test

1.

ACTIVE DTC

Turn the ignition on.

With the DRB, erase the FCM DTC’s.

Turn the ignition off then turn the ignition on and wait approximately 1 minute.

With the DRB, read the FCM DTC’s.

Did this DTC reset?

Yes

>> Replace the Front Control Module in accordance with the service information.

Perform BODY VERIFICATION TEST - VER 1. (Refer to BODY VERIFICATION TEST - VER 1.)

No

>> Test Complete.

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ELECTRONIC CONTROL MODULES - ELECTRICAL DIAGNOSTICS

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PCM MESSAGES NOT RECEIVED (FCM)

For a complete wiring diagram Refer to Section 8W.

•

When Monitored:
With the ignition on.

•

Set Condition:
The FCM does not receive any messages from the PCM for at least 5 seconds.

Possible Causes

(D25) PCI BUS CIRCUIT OPEN

POWERTRAIN CONTROL MODULE POWER AND GROUND

FRONT CONTROL MODULE

Diagnostic Test

1.

CHECK THE STATUS OF THE PCM ON THE PCI BUS NETWORK

Turn the ignition on.

With the DRB, enter System Monitors then J1850 Module Scan.

Is the PCM active on the bus?

Yes

>> Erase the DTC, if the DTC resets replace the Front Control Module in accordance with the service infor-

mation.

Perform BODY VERIFICATION TEST - VER 1. (Refer to BODY VERIFICATION TEST - VER 1.)

No

>> Go To 2

2.

ATTEMPT TO COMMUNICATE WITH THE PCM

With the DRB, attempt to communicate with the PCM.

Was the DRB able to communicate with the PCM?

Yes

>> Go To 3

No

>> Refer to the table of contents and perform the related symptom.

Perform BODY VERIFICATION TEST - VER 1. (Refer to BODY VERIFICATION TEST - VER 1.)

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ELECTRONIC CONTROL MODULES - ELECTRICAL DIAGNOSTICS

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PCM MESSAGES NOT RECEIVED (FCM) (CONTINUED)

3.

CHECK THE (D25) PCI BUS CIRCUIT FOR AN OPEN

Turn the ignition off.

Disconnect the PCM harness connector.

CAUTION: If the vehicle is equipped with an NGC controller, do
not probe the PCM harness connectors. Probing the PCM har-
ness connectors will damage the PCM terminals resulting in poor
terminal to pin connection. Install miller special tool #8815 to per-
form diagnosis.
Disconnect the DRB from the DLC.

Measure the resistance of the PCI Bus circuit between the PCM con-
nector (from special tool #8815 if NGC) and the DLC.

Is the resistance below 5.0 ohms?

Yes

>> Replace and program the PCM in accordance with the

service information.

Perform the appropriate VERIFICATION TEST.

No

>> Repair the PCI Bus circuit for an open.

Perform BODY VERIFICATION TEST - VER 1. (Refer to
BODY VERIFICATION TEST - VER 1.)

DR/DH

ELECTRONIC CONTROL MODULES - ELECTRICAL DIAGNOSTICS

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