P0643 Sensor Reference Voltage 1 Circuit High

P0643 Code - Set condition with the ignition on, the Powertrain Control Module (PCM) detects that the 5-volt supply circuit or the 5-volt supply circuit voltage is above the maximum acceptable value. ETC light is flashing.

P0643


Possible causes P0643 Code

  • 5-volt supply circuit shorted to voltage
  • 5-volt supply circuit shorted to voltage
  • Sensor shorted internally
  • Powertrain Control Module (PCM)

Diagnose P0643 Code


Step 1. Active DTC
Improperly installed aftermarket accessories can cause this DTC to set. Check for any improperly installed aftermarket accessories before continuing with this test. Turn the ignition on for at least 60 seconds, with the scan tool read active DTCs.

Is the DTC active at this time?

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

Step 2. Check the 5-volt supply circuit and the 5-volt supply circuit for a short to voltage
Turn the ignition off, disconnect all the sensor harness connectors that share the 5-volt supply circuit. Disconnect the APP sensor harness connector. Improperly installed aftermarket accessories can cause this DTC to set. Check for wiring added by customer. Ignition on engine not running, measure the voltage on the 5-volt supply circuit at the CKP sensor harness connector.

Is the voltage reading above 5.2 volts?

Yes, repair 5-volt supply circuit or the 5-volt supply circuit for a short to voltage.
No, go to step 3.

Step 3. Powertrain Control Module (PCM)

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