What this code means

The PCM detected that the 5-volt reference B circuit voltage is out of tolerance. This is a separate 5V reference circuit from P1635 and feeds a different set of sensors.

Symptoms

• Check Engine Light
• Engine stalling
• Multiple sensor DTCs
• Poor drivability
• Loss of power

Common causes

• Short to ground in a connected sensor circuit
• Damaged sensor wiring
• Faulty sensor on this reference
• PCM 5V reference driver failure

Diagnostic steps

1. Measure 5V reference 2 voltage
2. Disconnect sensors one at a time on this circuit
3. Inspect wiring for shorts
4. Test PCM output

Repair notes

Same diagnostic approach as P1635. Disconnect sensors one at a time to isolate the shorted circuit.

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