Checking the L Signal from the Generator (GEN) Charge Regulator

Checking the L signal from the generator (GEN) charge regulator

Checking the L signal from the generator (GEN) charge regulator

Warning! If the engine cooling fan (FC) is running, wait until it has stopped.




- Ignition on.
Read off the status of the L signal.
The L signal between the governor and the central electronic module (CEM) is used both to pre-magnetize the generator (GEN) and to provide a signal to the central electronic module indicating that the generator (GEN) is not charging when the engine is running. For information about the L signal, see Diagnostic functions Diagnostic Functions.
When the connector for the L signal is disconnected at the generator (GEN) the value should read less than 0.2 V with the ignition on. Disconnect the connector for the L signal from the generator (GEN). The value of the L signal must then change to greater than 0.8 V.

Hint: OnD5252Tengines the wiring for the L signal and DF signal are mounted in a common two pin connector. See the L and DF markings on the rear face of the generator (GEN).

Note! Diagnostic trouble codes (DTCs) may be stored in the central electronic module (CEM) when the L signal is disconnected. Erase any stored diagnostic trouble codes (DTCs) after fault-tracing.









Is the value OK?

Yes - No Fault Found

No - Checking wiring and terminals

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Checking wiring and terminals
Check the generator (GEN) connector for the L signal, connector A for the central electronic module (CEM) and the connector between them. Check for contact resistance and oxidation.
Check the signal cable between the generator (GEN) connector for the L signal terminal #L and central electronic module (CEM) terminal #A5 (#A5). Check for an open-circuit. Check for a short-circuit to ground. Check for a short-circuit to supply voltage.

Hint: Switch off the ignition. Read off the status of the L signal.
If the value continually displays greater than 0.8 V regardless of whether the connector is connected or not, there is an open-circuit or short-circuit to supply voltage.
If the value continually displays less than 0.2 V regardless of whether the connector is connected or not, there is a short-circuit to ground.

Warning! If the engine cooling fan (FC) is running, wait until it has stopped.

Remedy as necessary.

Other information
- To connect the breakout box to the central electronic module (CEM), see Connecting the breakout box Connecting the Breakout Box, Central Electronic Module (CEM)
- For information about central electronic module signals, see Signal specification Pinout Values and Diagnostic Parameters
- To fault-trace the wiring and terminals, see Checking wiring and terminals Checking Wiring And Terminals.










Continue - Verification

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Verification




Verification

Verification

Hint: After carrying out the repair, check that the fault has been remedied.








- Ignition off
- Reinstall the connectors, components etc.
- Ignition on.
Read off the status of the L signal.
The L signal between the governor and the central electronic module (CEM) is used both to pre-magnetize the generator (GEN) and to provide a signal to the central electronic module indicating that the generator (GEN) is not charging when the engine is running. For information about the L signal, see Diagnostic functions Diagnostic Functions.
When the connector for the L signal is disconnected at the generator (GEN) the value should read less than 0.2 V with the ignition on. Disconnect the connector for the L signal from the generator (GEN). The value of the L signal must then change to greater than 0.8 V.

Note! Diagnostic trouble codes (DTCs) may be stored in the central electronic module (CEM) when the L signal is disconnected. Erase any stored diagnostic trouble codes (DTCs) after fault-tracing.









Is the value OK?

Yes - VERIFIED

No - VERIFICATION FAILED

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VERIFIED - Fault Found

VERIFICATION FAILED - Fault-tracing information

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Fault-tracing information




Information

Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.

Do you want to exit fault-tracing?

Yes - FAULT-TRACING FAILED

No - Attempt New Test

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FAULT-TRACING FAILED - FAULT-TRACING FAILED

Attempt New Test - Checking the L signal from the generator (GEN) charge regulator

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