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Questions and Answers

Ford Taurus DTCs 326, 327, 335

Q. I have a question about my car.

  • 1995 Ford Taurus SE
  • 3.8 liter fuel injected V-6
  • 69,000 miles
  • Automatic transmission
  • ABS, P/S, cruise control
Ford Taurus DTCs 326, 327, 335, 536, 521

For weeks now, my check engine light would come on and go off randomly, and for periods of time ranging from 3 seconds to 2 hours. Mostly shorter times.

I borrowed a code reader and retrieved some codes. So far so good. Now I don't know what to do about the codes, or what action I need to take. Here's what I got:

KOEO (Key ON, Engine Off):

  • Code #327 - EGR Valve Position (EVP) sensor, Pressure Feedback EGR (PFE) sensor or EGR Pressure Transducer (EPT) signal voltage too low.
  • Code #335 - Pressure Feedback EGR(PFE) sensor or EGR Pressure Transducer(EPT) - signal voltage higher or lower than expected.

KOER (Key ON, Engine Running)

  • Code #326 - Pressure Feedback EGR (PFE) sensor or EGR Pressure Transducer (EPT) - signal voltage lower than expected.
  • Code #536 - Brake On-Off (BOO) switch - circuit failure or not activated during engine run self-test.
  • Code #521 - Power Steering Pressure Switch (PSPS) - open connection circuit failure.

Those are all the codes I received. Amazingly with all of this, my car has suffered no noticeable problems. Runs great, even gets good mileage. No brake or power steering issues. Flawlessly working car.

My question was mainly for the PFE & EGR problem, since 3 error codes point to that. I'm not sure what the others mean, or if they're vital. Any advice is very much appreciated. Thanks for your time.

Danny
Tracy, CA

A. Here are the code descriptions and possible causes. There are detailed diagnostic procedures and you can get them from the MOTORS Manuals at the public library's reference section or Alldata.

DTC 327 indicates the Pressure Feedback EGR (PFE) / Differential Pressure Feedback EGR (DPFE) sensor signal is less than the Self-Test minimum value of 0.2 volt.

Possible causes:

  • Damaged PFE/DPFE sensor.
  • Open harness circuits.
  • Shorted harness circuits.
  • Damaged Powertrain Control Module (PCM).

DTC 335 indicates the Pressure Feedback EGR (PFE) / Differential Pressure Feedback EGR (DPFE) sensor is out of Self-Test range.

Possible causes:

  • Damaged PFE/DPFE sensor.
  • Obstructed pressure inlet hose(s).
  • Garage exhaust ventilation system affecting PFE/DPFE sensor operation.

NOTE: PFE/DPFE system can sense a lack of pressure in the vehicle exhaust system. An efficient garage exhaust ventilation system that is installed during Key On Engine Off (KOEO) Test Mode may generate a DTC 335.

DTC 326 indicates the Pressure Feedback EGR (PFE) circuit voltage is lower than expected at zero EGR Vacuum Regulator (EVR) duty cycle.

Possible cause:

  • Obstructed vacuum hose.
  • Contaminated EVR filter.
  • Damaged EGR valve.
  • Damaged EVR solenoid.
  • Garage exhaust ventilation system.

NOTE: PFE system can sense a lack of pressure in the vehicle exhaust system. An efficient garage exhaust ventilation system that is installed during Key On Engine Running (KOER) Self-Test may generate a DTC 326.

DTC 536 indicate that when the brake pedal was depressed and released during the Key On Engine Running (KOER) Self-Test, the Brake On/Off (BOO) signal did not cycle high and low.

Possible causes:

  • Brake pedal not depressed and released during the KOER Self-Test.
  • Brake pedal depressed during entire KOER Self-Test.
  • Open BOO/stop lamp circuit.
  • Short to GROUND or POWER.
  • Damaged brake switch.
  • Damaged Powertrain Control Module (PCM).

DTC 521 indicates that the PSP switch did not change states due to the switch staying open or closed.

Possible causes:

  • Damaged PSP switch.
  • Open or grounded harness circuit.
  • Damaged Powertrain Control Module (PCM).
  • Wheel turned, not centered.

NOTE: Some vehicles are equipped with a Power Steering Pressure (PSP) switch software strategy, but do not have hardware released for the engine/vehicle application.

When Diagnostic Trouble Code (DTC) 521 is received in Key On Engine Running (KOER) , check to see if the vehicle is equipped with PSP switch. If not, disregard servicing DTC 521. Return to Diagnostic Routines to service other DTCs.

Basically you can ignore DTC 521 and DTC 536 since you probably did not perform the requirements for a proper test.

On the face of it, it seems the PFE/DPFE sensor has gone bad. Of course you should check vacuum lines and electrical connectors to be sure they are properly routed and connected.

Additional Information provided courtesy of AllDATA

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