DL25 - Check Exhaust Restriction

Diagnostic Trouble Code (DTC) 336 indicates the Pressure Feedback EGR (PFE) circuit voltage is higher than expected at zero EGR Vacuum Regulator (EVR) duty cycle.

DTC 337 indicates the PFE circuit voltage is above the Self-Test maximum. Possible causes:

- Restricted exhaust system. Damaged PFE sensor or Powertrain Control Module (PCM).

- Open harness circuits.

- Shorted harness circuits.

- Attach vacuum gauge to intake manifold source.

- Hook up tachometer.

- Observe the vacuum gauge needle while performing the following:

- Start engine and gradually increase the rpm from base idle to 2000 rpm with the transmission in NEUTRAL.

- Observe the rate of speed of the vacuum gauge needle as it falls and rises while maintaining the increased engine rpm and also note final vacuum reading.

NOTE: On a non-restricted system, the vacuum gauge needle will drop to zero and then quickly return to normal (above 16 in.). On a restricted system, the vacuum gauge needle will slowly drop to zero and slowly increase as rpm is maintained. The rate of speed at which the vacuum gauge needle returns to normal is much slower on a restricted system.

- Is the rate of speed the vacuum gauge needle returns to normal quick and a (minimum) vacuum of 16 inches reached?

Yes -- No restriction in the exhaust system. Go to DL26. DL26 - Check PFE Signal Voltage

No -- Refer to Exhaust Systems for further diagnosis.