Powertrain Controls - ECM/PCM

Diagnostic Trouble Code (DTC) 32 - Part 1 Of 2:

Diagnostic Trouble Code (DTC) 32 - Part 2 Of 2:

EGR Circuit:

***FOR UPDATED INFORMATION NOT INCLUDED HERE, REFER TO TECHNICAL SERVICE BULLETIN # 57-65-17A, DATED JUNE, 1996***

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 439. 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.

Pressure Chart:

DIAGNOSTIC TROUBLE CODE (DTC) 32 WILL SET WHEN
Vehicle speed between 16-32 mph, vehicle coasting, throttle angle 0%, transmission in 3/4 gear, Manifold Absolute Pressure (MAP) within range shown in table in accompanying image (depends on altitude), no change in A/C status, DTCs 21, 22, 24, 33, 34 not set, all conditions met for 2.5 seconds, and the PCM does not detect at least 1.3 kPa (0.2 psi) change in MAP when it commands EGR "ON" within the 1.5 second period of the test.

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

DTC CHART TEST DESCRIPTION
Numbers below refer to circled numbers 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 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 scan tool 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 gage and at the vacuum gage installed in place of the EGR valve.

3. Exiting "Field Service" will de-energize the EGR solenoid valve. The vacuum gage should bleed off through a vent in the solenoid valve. The pump gage may or may not bleed off but this does not indicate a problem.

DIAGNOSTIC AIDS
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.

Vacuum lines should be thoroughly checked for proper routing. Vacuum source goes to orifice side of the solenoid valve. Refer to underhood "Vehicle Emissions Control Information" label.

A leaking or plugged EGR valve pipe may cause faulty EGR operation.