Pinpoint Test W: Dual Generator Lower Circuit Fault Detected (P1149)

Pinpoint Test






Pinpoint Test W: Dual Generator Lower Circuit Fault Detected (P1149)

Refer to Wiring Diagram Set 12, Charging System for schematic and connector information. Diagrams By Number

Normal Operation

The generator output is determined by the voltage of the A circuit 35 (OG/LB). The A circuit voltage is compared to a set voltage internal to the voltage regulator and the voltage regulator controls the generator field current to maintain the correct generator output. The set voltage varies with temperature and is typically higher in cold temperatures and lower in warm temperatures.

This pinpoint test is intended to diagnose the following:
- I circuit open or short to voltage
- Lower generator



PINPOINT TEST W: DUAL GENERATOR LOWER CIRCUIT FAULT DETECTED (P1149)

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W1 CHECK THE LOWER GENERATOR I CIRCUIT 1185 (YE) OR CDC47 (WH) FOR A SHORT TO VOLTAGE


- Ignition OFF.
- Disconnect: PCM C1381e.
- Disconnect: Lower Generator C1251a.
- Ignition ON.
- With the Key ON Engine OFF (KOEO), measure the voltage between the PCM C1381e-4, circuit 1185 (YE), harness side and ground.




- Is the voltage greater than 0 volt?

Yes
REPAIR the I circuit 1185 (YE)/CDC47 (WH). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

No
GO to W2.

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W2 CHECK THE LOWER GENERATOR I CIRCUIT 1185 (YE) OR CDC47 (WH) FOR VOLTAGE


- Ignition OFF.
- Connect: PCM C1381e.
- Start the engine.
- NOTE: After starting the engine, wait at least 2 minutes for the glow plugs to stop cycling. If the glow plug system is cycling, the PCM will not provide voltage on the lower generator I circuit.
- With the engine running, measure the voltage between the lower generator C1251a-1, I circuit CDC47 (WH), harness side and ground.




- Is the voltage greater than 0 volt?

Yes
GO to W4.

No
GO to W3.

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W3 CHECK THE PCM OPERATION


- Ignition OFF.
- Connect the scan tool.
- Ignition ON.
- With the KOEO, carry out a glow plug test with the scan tool. Refer to Computers and Control Systems Information. Measure the voltage at the lower generator C1251a-1, I circuit CDC47 (WH) harness side and ground while carrying out the glow plug test.




- Is the voltage greater than 0 volt with the glow plugs on?

Yes
GO to W4.

No
INSTALL a new lower generator. REFER to Generator - Diesel Engines, Dual Generators . CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

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W4 CHECK FOR CORRECT PCM OPERATION


- Disconnect all of the PCM connectors.
- Check for:
- corrosion.
- pushed-out pins.
- Connect all of the PCM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?

Yes
INSTALL a new PCM. REPEAT the self-test. TEST the system for normal operation.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

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