LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 1997 >> C3500 HD 7.4 J, Automatic >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 3 (Engine Controls - Tests W/Codes - 6.5L) >> Diagnostic Trouble Codes >> DTC P1409 - EGR Vacuum System Leak >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different variant/trim than selected.
  1. Perform Powertrain ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING - 6.5L DIESEL article. Then go to next step.
  2. Install vacuum gauge in place of EGR valve. Start engine and operate at idle. Apply parking brakes and block drive wheels. Place transmission in Drive. Observe vacuum gauge. If vacuum reading is 5-7 in. Hg, go to step 4). If vacuum is not present, to next step.
  3. Turn ignition off. Disconnect vacuum hose to EGR vent solenoid. Install vacuum gauge to EGR vent solenoid hose. Start and operate engine at idle, with transmission in Drive. Observe vacuum gauge. If vacuum is present, go to step 7). If is not present, go to step 5).
  4. Turn ignition off. Install a hand-held vacuum pump to EGR valve. Apply 15 in. Hg to EGR valve. If EGR valve holds vacuum, go to step 6). If EGR valve does not hold vacuum, go to step 11).
  5. Check main vacuum source at solenoid assembly. If vacuum reading is greater than or equal to 15 in. Hg, go to step 10). If vacuum reading is less than 15 in. Hg, go to step 8).
  6. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
  7. Check for restricted or leaky vacuum hose from solenoid to EGR valve. Check for faulty EGR vent solenoid. Repair as necessary. After repairs, go to step 12). If vacuum hoses or EGR vent solenoid are okay, go to step 10).
  8. Check for leaking or deformed vacuum hose to vacuum pump. Repair as necessary. After repairs, go to step 12).
  9. Replace vacuum pump. After replacing vacuum pump, go to step 12).
  10. Repair leaking or deformed vacuum hoses at EGR solenoid, or faulty EGR solenoid. Repair or replace as necessary. After repairs, go to step 12).
  11. Replace EGR valve. After replacing EGR valve, go to next step.
  12. After repairs, reset EGR Adaptive Learn Matrix (ALM) cells using scan tool. After resetting EGR ALM cells, go to next step.
  13. Using scan tool, select CLEAR INFO. Start and warm engine to normal operating temperature. Test drive vehicle. Select DTC, SPECIFIC, then enter DTC P1409. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).
  14. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
scientia non olet · About LEMON Manuals