Dodge Ram Truck 1500-2500-3500. Manual — part 2012

ENGINE GAUGE RX FAILURE

For a complete wiring diagram Refer to Section 8W.

•

When Monitored:
With the ignition on.

•

Set Condition:
The Powertrain Control Module (PCM) (for gasoline engines) or Engine Control Module (ECM) (for diesel
engines) broadcasts a message on the PCI Bus that provides battery voltage, battery temperature, and engine
coolant temperature. This DTC will set if the A/C Heater Control does not receive this message for more than
5 seconds.

Possible Causes

FAULTS PRESENT IN THE POWERTRAIN SYSTEM

PCM NOT BROADCASTING MESSAGE

ECM NOT BROADCASTING MESSAGE

A/C HEATER CONTROL NOT RECEIVING MESSAGE

Diagnostic Test

1.

VERIFY THAT THE ENGINE GAUGE RX FAILURE DTC IS ACTIVE

Turn the ignition on.

With the DRBIII

T

, erase HVAC DTCs.

Cycle the ignition switch and wait approximately 30 seconds.

With the DRBIII

T

, read active HVAC DTCs.

Does the DRBIII

T

display: Engine Gauge RX Failure?

Yes

>> Go To 2

No

>> A technician may not have erased this DTC following a module or PCI Bus repair. If possible, verify if

the vehicle was recently in for this type of service. Otherwise, visually inspect the related wiring harness
for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken,
bent, pushed out, and corroded terminals. Repair as necessary.

Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL
MODULES/FRONT CONTROL MODULE - DIAGNOSIS AND TESTING).

2.

CHECK FOR DTCS IN THE PCM OR ECM

With the DRBIII

T

, read PCM or ECM DTCs.

Does the DRBIII

T

display any DTCs?

Yes (Gasoline Engines)

Diagnose and repair the DTC(s). (Refer to 9 - ENGINE ELECTRICAL DIAGNOSTICS).

Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL
MODULES/FRONT CONTROL MODULE - DIAGNOSIS AND TESTING).

Yes (Diesel Engines)

Diagnose and repair the DTC(s). (Refer to 9 - ENGINE ELECTRICAL DIAGNOSTICS).

Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL
MODULES/FRONT CONTROL MODULE - DIAGNOSIS AND TESTING).

No

>> Go To 3

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HVAC - ELECTRICAL DIAGNOSTICS

DR/DH

ENGINE GAUGE RX FAILURE (CONTINUED)

3.

VERIFY THAT THE PCM OR ECM IS BROADCASTING THE MESSAGE ON THE PCI BUS

With the DRBIII

T

in HVAC, select Monitor Display and then select PCI Bus Messages.

From the list, select the following:

•

Battery Volts

•

Battery Temp

•

Coolant Temp

Does the DRBIII

T

display NO RESPONSE after any of these messages?

Yes (Gasoline Engines)

Perform the *No Response From PCM (PCI Bus) diagnostic procedure. (Refer to 8 - ELECTRICAL/
ELECTRONIC CONTROL MODULES - DIAGNOSIS AND TESTING).

Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL
MODULES/FRONT CONTROL MODULE - DIAGNOSIS AND TESTING).

Yes (Diesel Engines)

Perform the *No Response From ECM (PCI Bus) diagnostic procedure. (Refer to 8 - ELECTRICAL/
ELECTRONIC CONTROL MODULES - DIAGNOSIS AND TESTING).

Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL
MODULES/FRONT CONTROL MODULE - DIAGNOSIS AND TESTING).

No

>> Replace the A/C Heater Control in accordance with the Service Information.

Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL
MODULES/FRONT CONTROL MODULE - DIAGNOSIS AND TESTING).

DR/DH

HVAC - ELECTRICAL DIAGNOSTICS

24 - 49

EVAPORATOR TEMPERATURE SENSOR CIRCUIT OPEN

24 - 50

HVAC - ELECTRICAL DIAGNOSTICS

DR/DH

EVAPORATOR TEMPERATURE SENSOR CIRCUIT OPEN (CONTINUED)

For the Manual Temperature Control (MTC) circuit diagram (Refer to 24 - HEATING & AIR CONDITIONING - SCHE-
MATICS AND DIAGRAMS).

For a complete wiring diagram Refer to Section 8W.

•

When Monitored:
With the ignition on.

•

Set Condition:
If the A/C Heater Control senses voltage is greater than 4.9 volts on the (C21) Evaporator Temperature Sensor
Signal circuit.

Possible Causes

(C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE

(C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT OPEN

(C121) SENSOR GROUND CIRCUIT OPEN

EVAPORATOR TEMPERATURE SENSOR

A/C HEATER CONTROL

NOTE: This DTC must be active for the results of this test to be valid. Do not perform this test if this DTC
is stored. Refer to HVAC System Test for stored DTC test procedures.

Diagnostic Test

1.

CHECK (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE

Turn the ignition off.

Disconnect the A/C Heater Control C1 harness connector.

Turn the ignition on.

Measure the voltage of the (C21) Evaporator Temperature Sensor Sig-
nal circuit.

Is the voltage above 0.2 volts?

Yes

>> Repair the (C21) Evaporator Temperature Sensor Signal

circuit for a short to voltage.

Perform BODY VERIFICATION TEST – VER 1. (Refer to 8
-

ELECTRICAL/ELECTRONIC

CONTROL

MODULES/

FRONT CONTROL MODULE - DIAGNOSIS AND TEST-
ING).

No

>> Go To 2

DR/DH

HVAC - ELECTRICAL DIAGNOSTICS

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