For 1990-2009 cars

Schematic Reference: Engine Controls Schematics

### Circuit Description

Vacuum to the Exhaust Gas Recirculation (EGR) valve is controlled by the EGR vacuum control signal solenoid valve. 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 ECT sensor, the MAF sensor and RPM. The PCM uses engine coolant temperature (ECT) and intake air temperature (IAT) to determine when to enable the EGR system. If the ambient temperature is cool when the vehicle is started, IAT is below 15°C (59°F), the PCM will wait longer before enabling the EGR, the EGR will not be enabled until ECT reaches 82°C (180°F). In warmer ambient temperatures, the PCM will allow the EGR system to operate earlier in the warm up cycle [If IAT is above 15°C (59°F) at start up, EGR will be enabled when ECT reaches 60°C (140°F). EGR operation is prevented under the following additional conditions:

• | Transmission is in Park/Neutral

• | Throttle Angle is less than a predetermined value

• | At wide open throttle (WOT)

The PCM tests the EGR system operation during specific driving conditions.

### Conditions for Setting the DTC

Enabling Conditions:

• | DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0601, P0719, P0724 not set.

• | Coolant above 27°C (81°F)

• | Vehicle speed above 14 mph

• | Baro above 95 kPa

• | RPM between 500 and 900

• | IAC steady

• | MAP less than 24 kPa

• | A/C clutch, TCC, Brake switch, no transitions

Test Conditions:

Decel Mode Test

• | TP Sensor below 1%

• | Not in DFCO

• | EGR duty cycle = 0%

• | The expected change in MAP is less than a predetermined amount when the PCM commands EGR ON during the test.

• | MAP within the range shown in the table (depends on altitude) and steady.

Baro (kPa) | Map Range for Test (kPa)
--- | ---
100 | 30 | 60
95 | 25 | 55
90 | 20 | 50
85 | 15 | 45
80 | 10 | 40

### Action Taken When the DTC Sets

• | The PCM will illuminate the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.

• | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and/or Failure Records.

• | The injector will be disabled for the entire ignition cycle.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.

• | A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.

• | A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | PCM battery voltage is interrupted.

• | Using a Scan tool.

### Diagnostic Aids

• | Suction from shop exhaust hoses can alter back pressure and may affect the operation of the EGR valve during in-stall testing. This DTC can be set by a leaking exhaust system because an exhaust leak alters back pressure. Thoroughly check the exhaust system for leaks. Refer to Section 6F, Exhaust System.

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

• | Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame and/or Failure Records data can be useful in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that were noted. This will isolate when the DTC failed.

• | A leaking EGR valve pipe assembly will cause an exhaust leak and can reduce EGR flow volume. Refer to Section 6A, Engine On-Vehicle Service if this condition is noted.

For intermittents, refer to Symptoms .

### Test Description

Number(s) below refer to step numbers on the diagnostic table.

1. Intake Passage: Turn the engine OFF. 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. Refer to Exhaust Gas Recirculation (EGR) System for more information.

   Exhaust Passage: With the EGR valve still removed, plug the intake side hole with a suitable stopper. With the exhaust side hole open and the engine running, check for the presence of exhaust gas. If no exhaust gas is present, the EGR exhaust side passage in the intake manifold is restricted. Refer to Exhaust Gas Recirculation (EGR) System for more information.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Start and idle the engine until normal operating temperature is reached.
2. Using the scan tool, command the EGR Duty Cycle to 100% and then back to 0%.

Does the engine RPM decrease and/or the engine idle roughly with an EGR Duty Cycle of 100% and then Engine RPM/idle quality return to normal when the duty cycle is returned to 0%?

--

Go to Step 3

Go to Step 4

3 |

1. Turn the ignition ON, engine OFF, review Freeze Frame and/or Failure Records data for this DTC and note parameters.
2. Turn the ignition OFF for 15 seconds.
3. Start the engine and operate the vehicle within the conditions required for this diagnostic to run, and as close to the conditions recorded in Freeze Frame/Failure Records as possible. Special operating conditions that need to be met before the PCM will run this diagnostic, where applicable, are listed in Conditions for Setting the DTC.
4. Using the scan tool, select DTC, Specific, then enter the DTC number which was set.

Does the scan tool indicate that this diagnostic failed this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4 | Manually lift the EGR valve diaphragm. Does the engine RPM decrease and/or the engine idle roughly? | -- | Go to Step 5 | Go to Step 10
5 |

1. Disconnect the vacuum harness at the solenoid valve.
2. Connect a vacuum gauge to the manifold side of the harness and check the vacuum supply to the solenoid valve.

Is the vacuum greater than the minimum value shown, at 2000 RPM?

25 kPa (7 inch Hg)

Go to Step 6

Go to Step 11

6 |

1. Turn the engine OFF.
2. Rotate the vacuum harness and connect only the manifold vacuum side to the solenoid valve.
3. Connect a vacuum gauge to the other port on the solenoid valve.
4. Start the engine.
5. Using the scan tool, command the EGR solenoid valve ON and OFF while observing the vacuum gauge.

Does the vacuum gauge indicate vacuum when the solenoid is ON and bleed off when the solenoid is OFF?

--

Go to Step 7

Go to Step 13

7 |

1. Reconnect the vacuum harness to the solenoid valve.
2. Using the scan tool, command the EGR solenoid valve ON and OFF while observing the vacuum gauge.

Does the vacuum gauge indicate vacuum when the solenoid is ON and bleed off when the solenoid is OFF?

--

Go to Step 8

Go to Step 12

8 |

1. Turn the ignition OFF.
2. Connect a vacuum pump to the EGR valve.
3. Observe the EGR valve diaphragm while applying vacuum.

Does the diaphragm move freely and hold vacuum for at least 20 seconds?

--

Go to Step 9

Go to Step 14

9 |

1. Apply 34 kPa (10 inch Hg) vacuum to the EGR valve.
2. Start the engine and immediately observe the gauge on the vacuum pump.

Does the EGR valve diaphragm move to the seated position and vacuum drop from the pump gauge while starting the engine?

--

Go to Step 15

Go to Step 14

10 | Repair plugged or restricted EGR passages. Refer to Exhaust Gas Recirculation (EGR) System for more information. Is the action complete? | -- | Go to Step 16 | --
11 | Repair the plugged vacuum port or faulty vacuum line. Is the action complete? | -- | Go to Step 16 | --
12 | Repair the faulty vacuum line to the EGR valve. Is the action complete? | -- | Go to Step 16 | --
13 | Replace the solenoid valve. Is the action complete? | -- | Go to Step 16 | --
14 | Replace the EGR valve. Is the action complete? | -- | Go to Step 16 | --
15 | Check for any of the following conditions which may cause insufficient EGR flow:

• | Partially clogged EGR passages

• | Restricted or damaged EGR pipe

• | Non OEM, modified or faulty exhaust system components

Is the action complete?

--

Go to Step 16

--

16 |

1. Using the scan tool, select DTC, Clear Info.
2. Start the engine and idle at normal operating temperature.
3. Select DTC, Specific, then enter the DTC number which was set.
4. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 17

Go to Step 2

17 | Using the scan tool, select Capture Info, Review Info. Are any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK