Diesel Data: Automotive Repair

P1406















Circuit Description

This diagnostic test checks for a malfunction in the circuitry and hardware of the Exhaust Gas Recirculation (EGR) valve. This diagnostic test runs 3 tests to check the EGR valve power and feedback circuits and controllability of the valve. If any test fails DTC P1406 will set.


Conditions for Setting the DTC

Test Condition

Ignition voltage 11 volts or greater.

Failure Conditions

^ TEST 1

- Closed EGR pintle position is 0.18 volts or less

OR

- Closed EGR pintle position is 2.06 volts or more.

^ TEST 2

Maximum change in desired EGR position is less than 0.10 volts and pintle position error is greater than 0.20 volts for 1 second.

^ TEST 3

Desired EGR position is 0 and EGR pintle position is 0.40 volts or more for at least 10 seconds twice.

Action Taken When the DTC Sets

^ PCM disables the EGR solenoid for the ignition cycle.

^ Transaxle shift adapts are maintained at current levels.

^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.

^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records.


Conditions for Clearing the MIL/DTC

^ The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.

^ A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.

^ A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test.

^ PCM battery voltage is interrupted.

^ Using a Scan tool.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

2. Checking if EGR valve feedback is valid with EGR OFF.

3. With the EGR valve OFF, the feedback should be 1.0 volt or less.

4. With the EGR valve commanded to 50%, the EGR pintle position should be between 2.0 and 3.0 volts.

5. With the EGR valve commanded on full, the EGR pintle position should be above 4.0 volts.

6. The DTC P1406 Freeze Frame or Failure Rec. (EGR pintle position) display can help determine the root cause even if the problem cannot be reproduced. If a low pintle position is recorded in the snapshot, that means a low feedback circuit voltage caused the DTC to set.

7. The DTC P1406 Freeze Frame or Failure Rec. (EGR pintle position) display can help determine the root cause even if the problem cannot be reproduced. If a high pintle position is recorded in the snapshot, that means a high feedback circuit voltage (possibly open) caused the DTC to set. If an intermediate pintle position is recorded in the snapshot, that means the DTC was probably set because the PCM could not control the EGR solenoid either due to intermittents in the solenoid or a sticky EGR valve.

32. A high voltage reading on the 5 volt reference circuit could be caused by a short to voltage on another 5 volt reference circuit, some 5V Ref. circuits are shared inside the PCM, or battery voltage bleeding onto the 5 volt reference circuit as in a defective Linear EGR Valve.