Dodge Ram Truck 1500-2500-3500. Manual — part 1275

*CHECKING A/C SYSTEM OPERATION WITH NO DTCS (CONTINUED)

12.

A/C SELECT SWITCH STATUS IN HVAC

Ignition on, engine not running.

With the scan tool in the HVAC, under the Monitors screen, read the A/C Select Switch state.

While monitoring the scan tool screen, turn the A/C switch on and off a few times.

Does the A/C Select State change on the HVAC Monitors screen.

Yes

>> Check for any related TSBs. Replace and program the PCM in accordance with the Service Information

as long as no BUS problems exist.

Perform BODY VERIFICATION TEST - VER 1.

No

>> Replace the A/C-Heater Control module.

Perform BODY VERIFICATION TEST - VER 1.

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ENGINE - ELECTRICAL DIAGNOSTICS - SRT-10

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*CHECKING CHARGING SYSTEM OPERATION WITH NO DTCS

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ENGINE - ELECTRICAL DIAGNOSTICS - SRT-10

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*CHECKING CHARGING SYSTEM OPERATION WITH NO DTCS (CONTINUED)

For the Engine circuit diagram (Refer to 9 - ENGINE - SCHEMATICS AND DIAGRAMS).

For a complete wiring diagram Refer to Section 8W.

Possible Causes

GENERATOR BELT CONDITION

RESISTANCE IN THE BATTERY POSITIVE CIRCUIT

(K125) GENERATOR FIELD SOURCE CIRCUIT OPEN

GENERATOR FIELD COIL HIGH RESISTANCE

(K20) GEN FIELD CONTROL CIRCUIT OPEN

RESISTANCE IN THE GENERATOR GROUND

PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)

Diagnostic Test

1.

TARGET CHARGING DIFFERS FROM ACTUAL CHARGING BY 1 VOLT

NOTE: Verify that the Battery is able to pass a load test before continuing.
Ignition on, engine not running.

With the scan tool, read the Battery voltage and record the results.

Measure Battery voltage between the Battery Positive and Negative Terminals and record the results.

Compare the two voltage readings.

Is the voltage difference less than one volt?

Yes

>> Go To 2

No

>> Go To 8

2.

RESISTANCE IN THE BATTERY POSITIVE CIRCUIT

Ignition on, engine not running.

Measure the voltage between the Generator B+ Terminal and the Battery+ Post.

CAUTION: Make sure all wires are clear of the engine’s moving parts.
Start the engine.

Is the voltage above 0.4 of a volt?

Yes

>> Repair the excessive resistance in the Battery Positive circuit between the Generator and Battery.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

No

>> Go To 3

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ENGINE - ELECTRICAL DIAGNOSTICS - SRT-10

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*CHECKING CHARGING SYSTEM OPERATION WITH NO DTCS (CONTINUED)

3.

(K125) GEN FIELD SOURCE CIRCUIT OPEN

Ignition on, engine not running.

Record all DTCs and freeze frame data, now erase Codes.

Carefully inspect all connectors for corrosion or spread terminals before continuing.

With the scan tool, actuate the Generator Field Driver.

Measure the voltage of the (K125) Generator Field Source circuit by backprobing the back of Generator Field har-
ness connector.

Is the voltage above 10.0 volts?

Yes

>> Go To 4

No

>> Repair the (K125) Generator Field Source circuit for an open or short to ground.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

4.

RESISTANCE IN THE GENERATOR GROUND

Start the engine.

Warm the engine to operating temperature.

CAUTION: Make sure all wires are clear of the engine’s moving parts.
Measure the voltage between the Generator case and Battery Negative Post.

Is the voltage above 0.1 of a volt?

Yes

>> Repair the excessive resistance in the Generator Ground circuit between the Generator Case and Bat-

tery Ground side.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

No

>> Go To 5

5.

GENERATOR FIELD COIL HIGH RESISTANCE

Turn the ignition off.

Disconnect the Generator Field harness connector at back of the Generator.

Measure resistance across the Generator Field Terminals at the Generator.

Is the resistance above 15 ohms?

Yes

>> Replace or repair the Generator as necessary.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

No

>> Go To 6

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ENGINE - ELECTRICAL DIAGNOSTICS - SRT-10

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