Part 1 of 2

DTC 32 Exhaust Gas Recirculation Circuit (Part 1 Of 2):

Exhaust Gas Recirculation (EGR) Schematic:

CIRCUIT DESCRIPTION
The Exhaust Gas Recirculation (EGR) valve vacuum is controlled by a Powertrain Control Module (PCM) controlled solenoid valve. The PCM will turn the EGR "ON" and "OFF" (duty cycle) by grounding CKT 435. The duty cycle is calculated by the PCM based on information from the engine coolant temperature, Manifold Absolute Pressure (MAP), vacuum, Throttle Position Sensor (TPS) and engine RPM. There should be no EGR when TPS input is below 3%, TPS indicating over 50% throttle, low vacuum, or low engine coolant temperature.
With the ignition "ON" and engine stopped, the EGR solenoid valve is de-energized and by grounding the diagnostic "test" terminal, the solenoid valve is energized.

DIAGNOSTIC TROUBLE CODE (DTC) 32 WILL SET WHEN
Operating in "Closed Loop," vehicle speed is greater than 50 mph at steady conditions, engine MAP vacuum is between 20 and 50 kPa for 3 minutes. This diagnosis is based on Oxygen Sensor (O2) voltage and short term fuel trim counts.

ACTION TAKEN (PCM will default to)
The PCM will retard ignition timing 3° while malfunction is being detected. The Malfunction Indicator Lamp (MIL) will become illuminated.

DTC 32 WILL CLEAR WHEN
A current DTC 32 will clear when O2S voltage and short trim fuel trim counts fall within the calibrated threshold. A history DTC 32 will clear after 50 consecutive ignition key cycles without a current DTC 32 being stored.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Intake Passage - Shut "OFF" engine and remove the EGR valve from the manifold. Plug the exhaust side hole with a suitable stopper. With the intake side hole open, attempt to start the engine. If the engine runs at a very high idle (up to 3000 RPM is possible) or starts and stalls, the EGR passages are not restricted. If the engine starts and idles normally, the EGR intake side passage in the intake manifold is restricted.
Exhaust Passage - With EGR valve still removed, plug the intake side hole with a suitable stopper. With the exhaust side hole open, check for the presence of exhaust gas. If no exhaust gas is present, the EGR exhaust side passage in the intake manifold is restricted.
2. By grounding the diagnostic "test" terminal, the EGR solenoid valve should be energized and allow vacuum to be applied to the gauge. The vacuum at the gauge may or may not slowly bleed off. It is important that the gauge is able to read the amount of vacuum being applied.
3. When the diagnostic "test" terminal is grounded, the vacuum gauge should bleed off through a vent in the solenoid valve. The pump gauge may or may not bleed off but this does not indicate a problem.
4. This test will determine if the electrical control part of the system is at fault or if the connector or solenoid valve is at fault.

DIAGNOSTIC AIDS
Suction from shop exhaust hoses can alter backpressure and may affect the operation of the EGR valve during in stall testing.
The PCM also monitors short term fuel trim during a DTC 32 test and must detect a change to pass the test. If short term fuel trim is at a fixed value (lean or rich) when a DTC 32 test is ran a DTC 32 may set.
Vacuum lines should be thoroughly checked for proper routing. Vacuum source goes to orifice side of the EGR solenoid valve.
When EGR diagnostic is run, Short Term (S.T.) fuel trim and O2S voltage are of short term duration. The Tech 1 scan tool may not capture data.