Diagnostic Aids

Perform this test when instructed by QUICK TEST. This test is only intended to diagnose:

• Wiring harness circuits (VREF, EGRV, EGRV VPWR, EGRA, EGRA VPWR, EGRP SIG, EGRP SIG RTN, EGRC VPWR, EGR/BARO SIG and EGR/BARO SIG RTN.
• EGR vacuum solenoid.
• EGR atmospheric solenoid.
• EGR Valve Position (EVP) sensor.
• EGR valve.
• EGR/Barometric Pressure (EGR/BARO) sensor.
• Faulty vacuum hose(s).
• Faulty Powertrain Control Module (PCM).

1)  DTC P0400 indicates lack of EGR flow. Possible causes for this faults is:

• Faulty EGR atmospheric solenoid.
• Faulty EGR atmospheric solenoid circuit(s).
• Faulty EVP sensor.
• Faulty EVP sensor circuits.
• Faulty EGR valve.
• Faulty EGR control solenoid.
• Faulty EGR control solenoid circuit(s).
• Faulty EGR vacuum solenoid.
• Faulty EGR vacuum solenoid circuit(s).
• Restricted exhaust.
• Faulty PCM.

Repeat QUICK TEST. If DTC P0106, P0107, P0108, P1400, P1401 or P1408 is present, EGR system damage is indicated. Perform appropriate DTC test and repeat QUICK TEST. If specified DTCs are not present, go to next step.

2) Check VPWR At EGR Control Solenoid  Turn ignition off. Disconnect EGR control solenoid. Turn ignition on. Measure voltage between VPWR terminal of EGR control solenoid wiring harness connector and chassis ground. If voltage is 10.5 volts or more, go to next step. If voltage is less than 10.5 volts, repair open VPWR circuit and repeat QUICK TEST.

3) Check EGR Control Solenoid Resistance  Turn ignition off. Disconnect EGR control solenoid wiring harness connector. Measure resistance between solenoid terminals. If resistance is 30-70 ohms, go to next step. If resistance is not 30-70 ohms, replace EGR control solenoid. Clear PCM memory and repeat QUICK TEST.

4) Check EGR Control Solenoid Circuit Resistance  Leave ignition off and EGR control solenoid disconnected. Measure resistance between test pin No. 98 (EGRC) and EGRC terminal at EGR control solenoid wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in EGRA circuit and repeat QUICK TEST.

5) Check EGR Control Circuits For Short To Ground Or Power  Leave ignition off and EGR control solenoid disconnected. Disconnect scan tool from DLC (if applicable). Measure resistance between test pin No. 98 and test pins No. 91 (SIG RTN), 51 and 103 (PWR GND) at breakout box. Measure resistance between test pin No. 98 and test pins No. 71 (VPWR), 90 (VREF), and 97 (VPWR) at breakout box. If each measurement is 10,000 ohms or more, go to next step. If any measurement is less than 10,000 ohms, repair short in EGR control circuit and repeat QUICK TEST.

6) Check EGR Control Solenoid Response  Leave ignition off. Disconnect vacuum hose from EGR control solenoid (from intake manifold reservoir). Connect vacuum pump to EGR control solenoid port. Disconnect vacuum hose from EGR/BARO sensor (from EGR control solenoid). Connect vacuum pump to hose. Inspect hoses for damage and repair if necessary. Turn ignition on. Momentarily jumper test pin No. 98 (EGRC) at breakout box to ground. Using vacuum pump, apply 10 in. Hg to EGR vacuum solenoid. Again, momentarily jumper test pin No. 98 (EGRC) at breakout box to ground. If vacuum signal is indicated (at any time) by vacuum gauge, EGR control solenoid is okay. Replace PCM and repeat QUICK TEST. If vacuum signal is not indicated by vacuum gauge, replace EGR control solenoid and repeat QUICK TEST.