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HOMESERVICE MANUALSGMC1984PICKUP K2500, 6.2 C, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMDIESEL CEC TESTINGEGR/EGR VENT CHECK
1984 GMC Pickup K2500, 6.2 C, Standard

EGR/EGR Vent Check

1984 GMC Pickup K2500, 6.2 C, StandardSECTION EGR/EGR Vent Check

The EGR solenoid controls the amount of vacuum to the EGR valve. The signal from the ECM is Pulse Width Modulated (PWM) which varies the on-off time (duty cycle) from 0-100 percent. Vacuum to EGR valve is controlled by EGR solenoid cycling. When EGR solenoid is on, there is no EGR vacuum.

The EGR vent solenoid operates to allow rapid venting of EGR vacuum to improve driveability and performance when the ECM recognizes the operating range for no EGR flow. When the solenoid is on, EGR vacuum is vented.

Both solenoids operate on 12 volts supplied by the ignition. The ECM supplies the ground to turn the solenoids on.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).
  1. This step checks for EGR vacuum at idle. Normally, there should be full EGR vacuum at idle (above 20 in. Hg).
  2. This step ensures ground in circuit would energize either solenoid. At idle, neither solenoid should be on. A test light on indicates a faulty ground in the circuit.
  3. This step checks for complete circuits to both solenoids. The test light should normally be on.
  4. In the 3.9k mode, the tester should turn the vacuum off to the EGR valve by ECM activation of the EGR vent solenoid. If vacuum is present, the ECM was not able to energize the EGR vent solenoid.
Fig 1: EGR/EGR Vent Check
G9488
RENDER: 1.0x

NO RELATED

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