Circuit Description
An exhaust gas recirculation (EGR) system is used in order to lower oxides of nitrogen (NOx) emission levels. The EGR system accomplishes this by recirculating small amounts of exhaust gas back into the combustion chamber. High combustion temperatures cause NOx. Combustion temperatures are reduced when the air/fuel mixture is diluted with the exhaust gases.
The EGR valve is designed to accurately supply exhaust gases to the engine without the use of intake manifold vacuum. The EGR valve controls the exhaust flow into the intake manifold from the exhaust manifold through an orifice with a powertrain control module (PCM) controlled pintle. The PCM controls the pintle position using inputs from the throttle position (TP) sensor, the manifold absolute pressure (MAP) sensor, and the engine coolant temperature (ECT) sensor. The PCM commands the EGR valve in order to supply the correct amount of exhaust gas recirculation for the current engine operating conditions. This can be monitored on a scan tool as the desired EGR position.
The PCM monitors the position of the EGR valve through a feedback signal. The PCM supplies a 5-volt reference circuit and a ground circuit to the EGR valve. A voltage signal representing the EGR valve pintle position is sent to the PCM from the EGR valve. This feedback signal can also be monitored on a scan tool and is the actual position of the EGR pintle. The actual EGR position should be near the desired EGR position.
Conditions for Running the DTC
| • | The ignition voltage is more than 11.7 volts. |
| • | The engine is running. |
Conditions for Setting the DTC
| • | The EGR feedback signal voltage is less than 0.14 volts. |
| • | All conditions are present for 5 seconds. |
Diagnostic Aids
| • | Poor connection at the PCM or EGR valve--Inspect the harness connectors for: |
| - | Backed out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | Poor terminal to wire connection |
| • | Refer to Connector Repairs in Wiring Systems. |
| • | Damaged harness--Inspect the wiring harness for damage. If the harness appears to be OK, connect a DMM and check the circuit continuity while moving connectors and wiring harnesses related to the EGR valve. A change in the DMM display will indicate the location of the malfunction. Refer to Connector Repairs in Wiring Systems. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Does the EGR position sensor remain close to the commanded state? | 0-100% | Go to Step 3 | Go to Step 4 | |
3 |
Does the DTC reset? | -- | Go to Step 4 | Go to Diagnostic Aids |
4 |
Does the scan tool indicate EGR position sensor near the specified value? | 100% | Go to Step 11 | Go to Step 5 |
5 |
Does the DMM display voltage near the specified value? | 5 V | Go to Step 9 | Go to Step 6 |
6 | With a DMM, test the EGR position sensor 5-volt reference circuit for an open or high resistance. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 7 |
7 | Test all 5-volt reference circuits for a short to ground. Refer to Wiring Repairs and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 8 |
8 | With a DMM connected between the EGR position sensor 5-volt reference circuit and the EGR position sensor ground circuit, observe voltage while disconnecting all sensors, one at a time, that use a 5-volt reference signal. A change in voltage indicates the faulty component. Replace that component as necessary. Refer to the appropriate replacement procedure Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 10 |
9 | With a DMM, test the EGR position sensor signal circuit for a short to ground, high resistance or an open. Refer to Wiring Repairs and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 10 |
10 | Inspect for poor connections at the PCM harness connector. Refer to Wiring Repairs and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13 |
11 | Inspect for poor connections at the EGR valve harness connector. Refer to Wiring Repairs and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 12 |
12 | Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
14 |
Does the DTC run and pass? | -- | Go to Step 15 | Go to Step 2 |
15 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
