P1406

Code P1406, EGR Valve Pintle Position Error (1 Of 2):

Code P1406, EGR Valve Pintle Position Error (2 Of 2):

Exhaust Gas Recirculation (EGR) Circuit:

*** This information has been updated according to Technical Service Bulletin #516525, dated May 1995.

CIRCUIT DESCRIPTION
The PCM constantly monitors the linear EGR valve pintle position sensor to ensure that the valve is responding properly to commands from the PCM.

DTC P14O6 WILL SET WHEN:
^ EGR pintle position signal indicates a voltage out of the normal range of the pintle position sensor, or a signal that is 10% greater or less than the PCM commanded position.
^ Either condition for up to 20 seconds.

ACTION TAKEN (PCM will default to):
If a current DTC P1406 sets during two consecutive key cycles, the PCM will illuminate the MIL (Service Engine Soon).

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Checks for an EGR valve sticking partially open or an incorrect pintle position sensor feedback signal.
2. Ensures that the PCM is capable of controlling EGR pintle position and is reading the pintle position feedback signal properly.
3. Checks the EGR valve driver in the PCM and CKT 435.
4. The checks on this page of the chart will diagnose an incorrect EGR pintle position sensor input signal. This test verifies a 5 volt reference at the EGR valve.
5. Ensures that CKT 1456 is not shorted to ground.
6. Checks CKT 1456 for an open.

DIAGNOSTIC AIDS
An intermittent may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside the insulation.

Check for:
^ Poor connection or damaged harness - Inspect PCM harness connectors for backed out terminals "RA16", "WC6", "WC1O", or "BF12", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
^ Sticking EGR valve - An EGR valve which intermittently sticks partially open or closed can cause DTC P1406 to be set, especially when the engine has reached normal operating temperatures and the EGR valve is hot. It may be possible to isolate this condition by observing "Desired EGR Pos." and "Actual EGR Pos." on the scan tool while operating the vehicle. If a large difference in the desired and actual positions is noted, replace the EGR valve.
^ Internally shorted EGR valve - An EGR valve which is internally shorted can cause the 5V reference circuit or the pintle position circuit to measure B+ all of the time. Measure the voltage on these two circuits with the ignition "ON". If they measure B+, disconnect the EGR valve and recheck the voltage reading. If the voltage goes back to normal, replace the EGR valve.
^ Intermittent test - If connections and harness check OK, monitor a digital voltmeter connected between affected terminals and ground while moving related connectors and wiring harness. If the failure is induced, the voltage reading will change.