Powertrain Controls - ECM/PCM

Diagnostic Trouble Code (DTC) 32:

DTC 32 Chart (2 Of 2):

EGR Control Circuit:

CIRCUIT DESCRIPTION
Vacuum to the Exhaust Gas Recirculation (EGR) valve is controlled by the EGR vacuum control signal solenoid valve. Ignition voltage is supplied directly to the solenoid valve on CKT 541. The Powertrain Control Module (PCM) controls the solenoid valve by providing the ground path through CKT 435. The vacuum signal to the EGR valve is regulated by varying the duty cycle ("on-time") of the solenoid valve. The duty cycle is calculated by the PCM based on data from the Engine Coolant Temperature (ECT) sensor, Mass Air Flow (MAF) sensor and RPM. If Intake Air Temperature (IAT) is below 15°C (59°F) when the vehicle is started, EGR will not be enabled until ECT is above 82°C (180°F).

If IAT is above 15°C (59°F) at start up, EGR will not be enabled until ECT is above 32°C (90°F). There should also be no EGR when in park/neutral or when Throttle Position (TP) sensor is below a specified value or at Wide Open Throttle (WOT). During specific driving conditions the PCM will test the EGR system.

DIAGNOSTIC TROUBLE CODE (DTC) 32 WILL SET WHEN
Vehicle speed between 16-50 MPH for Automatic Transmission (A/T) or 25-65 MPH for Manual Transmission (M/T), vehicle coasting A/T, throttle angle 0% A/T or throttle angle between 8% and 20% M/T, transmission in 3rd gear or higher, Manifold Absolute Pressure (MAP) within range as shown in table (depends on altitude), no change in A/C status, DTCs 21, 22, 24, 33, 34 not set, Barometric Pressure (BARO) greater than 80 kPa (depends on altitude), all conditions met for 2.5 seconds, and the PCM does not detect at least 1.0 kPa change in MAP when it commands EGR "ON" A/T or when the PCM commands the EGR "OFF" M/T within the 1.5 second period of the test.

ACTION TAKEN (PCM WILL DEFAULT TO)
The Malfunction Indicator Lamp (MIL) will illuminate.

CHART TEST DESCRIPTION, (1 OF 2)
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. The Tech 1 scanner actuates the EGR vacuum control signal solenoid valve when in the "Field Service" mode. The system should hold vacuum which should be indicated at the vacuum pump gauge and at the vacuum gauge installed in place of the EGR valve.
3. Exiting "Field Service" will de-energize the EGR: solenoid valve.
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.

CHART TEST DESCRIPTION, (2 OF 2)
Number(s) below refer to circled number(s) on the diagnostic chart.
1. The remaining test checks the ability of the EGR valve to interact with the exhaust system. This system uses a negative backpressure EGR valve which should hold vacuum with engine "OFF."
2. When engine is started, exhaust backpressure at the base of the EGR valve should open the valve's internal bleed and vent the applied vacuum allowing the valve to seat.

DIAGNOSTIC AIDS
The EGR circuit can be inoperative if the Park/Neutral (PNP) switch is misadjusted or faulty. The EGR is disabled when in park or neutral. To check PNP switch, refer to Diagnostic Charts/C Charts/Chart C-1A. Chart C-1A Park/Neutral Switch Diagnosis

Suction from shop exhaust hoses can alter backpressure and may affect the operation of the EGR valve during in stall testing. A DTC 32 can be caused by a leaking exhaust system. An exhaust leak will alter backpressure. Thoroughly check exhaust system for leaks.

During normal EGR valve operation, the movement of the EGR valve pintle is small.

It is important to determine whether or not the valve pintle moves and not how much it moves.

When TCC is enabled, EGR will be operating at a reduced duty cycle. A leaking or plugged EGR valve pipe may cause faulty EGR operation.