Powertrain Controls - ECM/PCM
Diagnostic Trouble Code 32 - 1 Of 3:
Diagnostic Trouble Code 32 - 2 Of 3:
Diagnostic Trouble Code 32 - 3 Of 3:
EGR Solenoid Valve:
CIRCUIT DESCRIPTION
The Engine Control Module (ECM) operates a solenoid valve to control the Exhaust Gas Recirculation (EGR) valve. This solenoid valve is normally closed. By providing a ground path, the ECM energizes the solenoid valve which then allows vacuum to pass to the EGR valve.
The ECM monitors EGR effectiveness by de-energizing the EGR control solenoid valve thereby shutting "OFF" vacuum to the EGR valve diaphragm. With the EGR valve closed, manifold vacuum will be greater than it was during normal EGR operation and this change will be relayed to the ECM by the MAP sensor. If the change is not within the calibrated window, a Diagnostic Trouble Code (DTC) 32 will be set.
The ECM will check EGR operation when:
^ Vehicle speed is above 50 mph.
^ Manifold Absolute Pressure (MAP) is as listed in table below (depends on altitude).
^ Throttle Position (TP) sensor is between 9% and 20%.
^ No change in throttle position while test is being run.
^ ECM commanded EGR to 100%.
BARO Pressure (kPa)
100 95 90 85 80
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MAP 40-60 35-55 30-50 25-45 20-40
(Test Pressure Range - kPa)
TEST DESCRIPTION
Numbers below refer to circled numbers on diagnostic chart part 1 of 3.
(Part 1 of 3)
1. Intake Passage: Shut "OFF" engine and remove the EGR valve from the manifold. Plug the exhaust side hole with a shop rag or suitable stopper. Leaving 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 gage. The vacuum at the gage may or may not slowly bleed off. It is important that the gage is a e to read the amount of vacuum being applied.
3 When the diagnostic "test" terminal is ungrounded, 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.
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.
5. EGR valves used with this engine are stamped on the top side of the valve with: (P) for Positive backpressure valves or (N) for Negative backpressure valves. Refer to Emission Control Systems/Exhaust Gas Recirculation/EGR Valve/Application and ID for additional information. EGR Valve
DIAGNOSTIC AIDS
Vacuum lines should be thoroughly checked for proper routing. Refer to underhood "Vehicle Emissions Control Information" Label.
TEST DESCRIPTION
Numbers below refer to circled numbers on diagnostic chart part 2 of 3.
(Part 2 of 3)
6. The remaining tests check the ability of the EGR valve to interact with the exhaust system. This system uses a positive backpressure EGR valve which will not hold vacuum until sufficient exhaust backpressure is at the base of the valve.
7. The EGR valve diaphragm should move when sufficient exhaust backpressure is present at the base of the valve and when vacuum is being supplied to the valve. Rapidly "snapping" the throttle from idle should provide sufficient exhaust backpressure to the base of the valve which will close an internal vacuum bleed. With the EGR valve's internal vacuum bleed closed, the "jumpered" vacuum supply can now lift the valve off its seat.
8. Excessive exhaust backpressure from bent or restricted exhaust system components could provide enough backpressure at the base of the EGR valve to close the valve's internal bleed and allow undesired EGR valve operation at idle.
9. Plugged EGR exhaust passages can block exhaust backpressure from reaching the EGR valve. With no EGR exhaust backpressure at the base of the valve, the valve's internal bleed will remain open and prevent vacuum from operating the valve.
DIAGNOSTIC AIDS
Suction from shop exhaust hoses can alter backpressure and may effect the functional check of the EGR valve.
TEST DESCRIPTION
Numbers below refer to circled numbers on diagnostic chart part 3 of 3.
(Part 3 of 3)
10. The remaining tests check 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."
11. 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.