P2504 Charging System Output High

P2504 code - The Alternator sense circuit input voltage (E) to the PCM exceeds the B+ (B) sensed by the PCM. Default action this DTC is a non MIL fault.

P2504 code

Possible causes P2504 code

- Open or high resistance between the alternator B+ terminal and the TIPM/BCM B+ terminal
- Resistance in the fused B+ circuit between the TIPM/BCM and the PCM
- Totally Integrated Power Module or Body Control Module (PCM)
- Powertrain Control Module (PCM)

Diagnostic test P2504 code

Step 1. Check for an active DTC
Inspect the vehicle for aftermarket accessories that may exceed the alternator system output.
Inspect and test battery with the midtronics battery tester or equivalent for a shorted or dead cell before continuing with this test.
This DTC does not necessary indicate on overcharging condition. It merely indicates that the alternator sense is greater than the alternator output back to the battery and PDC.

Start the engine, allow the idle to stabilize. With the scan tool read the active DTCs.

Is the DTC active?

Yes, go to step 2.
No, perform the PCM intermittent condition.

Step 2. Check the alternator output
With the scan tool, navigate to data display and monitor the target charging voltage. Using a voltmeter, measure the voltage between ground and the alternator output stud. The voltage reading at the alternator output stud should be within 0.2 volts of the target charging voltage.

Are the voltage readings within 0.2 volts of each other?

Yes, go to step 3.
No, replace the alternator.

Step 3. Check the alternator output circuit and system voltage
Using a voltmeter, back probe and measure the voltage between ground and the fused B+ circuit at the TIPM harness connector. Compare the voltage reading to the voltage at the alternator output stud.

Is the voltage within 0.2 volts of the measurement at the alternator output stud?

Yes, go to step 4.
No, repair the open or excessive in the alternator output circuit.

Step 4. Check the TIPM
Turn the ignition off, back probe the fused B+ circuit at the TIPM harness connector. Start the engine and allow it to idle. Using a voltmeter, measure the voltage between ground and the fused B+ circuit. Compare the voltage reading to the voltage at the alternator output stud.

Is the voltage within 0.2 volts of the measurement at the alternator output stud?

Yes, go to step 5.
No, check the fuse and terminals for signs of a spread terminal, corrosion or high resistance. If no problems are found, replace the TIPM.

Step 5. Check the fused B+ circuit voltage
Turn the ignition off, disconnect the PCM harness connector. Turn the ignition on, using a voltmeter measure the voltage between ground and the fused B+ circuit at the PCM harness connector.

Compare the voltage reading to the voltage at the alternator output stud. Approximately 2.0 Ohms of resistance in this circuit can drop the voltage by approximately 0.5 Volts.

Is the voltage within 0.2 volts of the measurement at the alternator output stud?

Yes, go to step 6.
No, repair the fused B+ circuit for high resistance.

Step 6. Check related PCM and component connections

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