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1999 CHEVROLET ASTRO

4.3L V6 Vortec•RWD•AUTOMATIC•gas
4 active safety recalls on this vehicle — view recalls
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Repairs0Labor564Torque4690Fluid7DTC687Battery1Maintenance0Recalls4
P1639high severityPowertrain

5 Volt Reference 2 Circuit

on 1999 Chevrolet Astro 4.3L V6 Vortec · RWD

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.

Other Powertrain codes on this vehicle

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