Circuit Description
The EGR flow is controlled by the vacuum actuated EGR valve. The EGR vent so l enoid purges to atmosphere the vacuum level at the EGR val ve actuator as commanded by the PCM. This is done when the EGR flow is desired to turn off quickly. When the PCM is commanding the EGR vent ON, the voltage potential of the circuit will be low (near 0 volts). When the PCM is commanding the EGR vent OFF, the voltage potential of the circuit will be high (near battery voltage). The primary function of the PCM in this circuit is to supply the ground for the EGR vent solenoid.
Conditions for Running the DTC
The ignition switch in the ON position.
Conditions for Setting the DTC
โข The voltage on the EGR vent control circuit is high (near battery voltage) when the EGR vent is requested ON.
or
โข The voltage on the EGR vent control circuit is low (near 0 volts) when the EGR vent is requested OFF.
Action Taken When the DTC Sets
โข The PCM illuminates the malfunction indicator
lamp (MIL) on the second consecutive drive
trip the diagnostic runs and fails.
โข The PCM records the operating conditions at the
time the diagnostic fails. The first time the
diagnostic fails, the Failure Records store this
information. If the diagnostic reports a failure on
the second consecutive drive trip, the Freeze
Frame records the operating conditions at the time
of failure and updates the Failure Records.
Conditions for Clearing the MIL/DTC
โข The PCM will turn the MIL off after three consecutive trips without a fault condition.
โข A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures
โข The use of a scan tool.
Diagnostic Aids
The scan tool has a 5 second ON time abort. The EGR vent solenoid can be commanded ON for as many times as needed, in 5 second intervals. Its possible other EGR DTCs may set along with DTC P1653. This diagnostic can be checked at key up. A quick operational check can be made by commanding the EGR vent solenoid ON and OFF with the scan tool while monitoring Actual EGR. Actual EGR will display BARO (approximately) when EGR solenoid is OFF.
The Adaptive Learn Matrix (ALM) is used to adjust the EGR vacuum control based on mass air flow (MAF). The ALM may change as a result of back pressure increases over the life of the vehicle or other engine system variations. The ALM is made up of sixteen cells (numbered from zero to fifteen) in which each cell covers a range of engine speed (RPM) and load (mm3).
An intermittent may be caused by the following:
โข Poor connections.
โข Rubbed through wire insulation.
โข Broken wire inside the insulation.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
2. Be sure that both the ON and OFF states are commanded. Repeat the commands as many times as necessary.
3. This check can detect a partially shorted coil which would cause excessive current flow. Leaving the circuit energized for 2 minutes a llows the coil to warm up. When warm, the coil may open (Amps drop to zero, or short (Amp draw greater than 0.75 A).
7. Listen for an audibl e click when the solenoid operates.
