Powertrain Controls - ECM/PCM
Code 32 - Exhaust Gas Recirculation (EGR) System:
Wiring Diagram For Code 32:
CODE 32 - EXHAUST GAS RECIRCULATION SYSTEM
CIRCUIT DESCRIPTION:
The ECM operates a solenoid to control the Exhaust Gas Recirculation (EGR) valve. This solenoid is normally closed. By providing a ground path, the ECM energizes the solenoid which then allows vacuum to pass to the EGR valve.
The ECM monitors EGR effectiveness by de-energizing the EGR control solenoid thereby shutting off vacuum to the EGR valve diaphragm. With the EGR valve closed and O2 sensor fluctuating normally, fuel integrator counts will be greater than they were during normal EGR operation. If the change is not within the calibrated window, a Code 32 will be set.
The ECM will check EGR operation when:
^ Vehicle speed is above 50 mph.
^ Engine vacuum is between 12.5 and 55 kPa.
^ No change in throttle position while test is being run.
*** UPDATED BY TSB # 91-149-6E DATED JANUARY 1991
Some 1987-91 light duty trucks may experience a possible Code 32 - EGR System Malfunction. The customer may not experience a change in performance or driveability with a Code 32 set. If normal EGR diagnostics do not reveal the cause for Code 32, the following steps should be taken to correct the condition:
Check the TCC (Torque Converter Clutch) engagement solenoid/wiring harness for a short.
1. Disconnect the TCC transmission connector from the left side of transmission.
2. Measure resistance between TCC transmission connector terminals "A" and "D" with a Digital Volt Ohm Meter. Solenoid resistance must measure between 20 to 25 ohms at 20~C (68~F). Resistance will be slightly higher if the transmission is at operating temperature. If the resistance is less than 20 ohms the TCC solenoid diode or wiring is shorted and the solenoid must be replaced.
3. With key on, using a DVOM check for voltage at pin "D" of the TCC wiring harness. Voltage should not be greater than 1 volt. If voltage exceeding 1 volt is present, circuit 422 is shorted to voltage and the short must be repaired.
Test operation of the TCC through the use of a scan tool connected to the vehicle ALDL connector. The following conditions must be satisfied when testing TCC operation.
^ Clear stored trouble codes
^ Engine at normal operating temperature and in closed loop.
^ Constant throttle position. TPS voltage = 1.3 volts. (minimum = 1.1 volts, maximum = 1.5 volts).
^ Vehicle speed = 45 mph (minimum = 35 mph, maximum = 55 mph).
^ Brake switch closed (brake pedal not applied).
^ 3rd or 4th gear.
Confirmation
The scan tool will display the ECM command for TCC engagement when the above conditions are satisfied. When the TCC engages there should be a decrease in engine speed by a minimum of 100 rpm. If the TCC operation is normal, it is not necessary to replace the solenoid assembly. After verification of TCC operation, check for stored trouble codes. If TCC fails to engage, refer to C-CHARTS TORQUE CONVERTER CLUTCH (TCC CLUTCH).
TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.
1. With the ignition "ON," engine stopped, the solenoid should not be energized and vacuum should not pass to the EGR valve. Grounding the diagnostic terminal will energize the solenoid and allow vacuum to pass to valve.
2. Checks for plugged EGR passages. If passages are plugged, the engine may have severe detonation on acceleration.
3. The "SERVICE ENGINE SOON" light should also flash while the diagnostic terminal is grounded. If the light does not flash, this may indicate that the quad-driver has been damaged by low resistance in the TCC circuit.
4. The vehicle must be driven during this test in order to produce sufficient engine load to operate the EGR. Lightly accelerating (approximately 1/4 throttle) will produce a large and stable enough reading to determine if the ECM is commanding the system "ON".
DIAGNOSTIC AIDS:
Before replacing ECM, use an ohmmeter and check the resistance of each ECM controlled relay and solenoid coil. For example TCC etc., refer to ECM QDR CHECK PROCEDURE. ALSO SEE ECM WIRING DIAGRAM for coil terminal identification of solenoid(s) and relay(s) to be checked. Replace any solenoid where resistance measures less than 20 ohms.