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Home >> Acura >> 1991 >> Integra LS, 2D Hatchback, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Code 12: EGR System

Code 12: EGR System

NOTE: For wiring diagrams, see WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section. For vacuum diagrams, see VACUUM DIAGRAMS article in the ENGINE PERFORMANCE Section.
  1. Turn ignition off. Remove HAZARD fuse in main fuse box for at least 10 seconds to reset ECU. Warm engine until cooling fan comes on. Observe CHECK ENGINE and LED lights. If lights are off, problem is intermittent.
  2. Check for poor and loose connections at EGR position sensor, connector C216 at right shock tower, connector C318 at left shock tower, control box and ECU. If CHECK ENGINE light is on and LED indicates Code 12, start engine. Disconnect vacuum hose No. 16 from EGR valve. Connect vacuum gauge to hose.
  3. If vacuum is present, disconnect 4-pin connector from control box. If no vacuum is present, go to next step. Check vacuum again on hose No. 16. If vacuum is present, check vacuum hose routing. If routing is okay, replace EGR control solenoid valve. If vacuum is not present, check for short or ground in Red wire between EGR control solenoid valve and ECU terminal A8. If wire is okay, substitute a known good ECU. If system operates properly, replace original ECU.
  4. If vacuum is not present during first vacuum test in step 3), install vacuum pump on EGR valve. With engine idling, apply 8 in. Hg to EGR valve. If engine does not stall and EGR valve does not hold vacuum, replace EGR valve.
  5. If engine stalls and EGR valve holds vacuum, disconnect 4-pin connector from control box. Measure voltage between Black/Yellow wire terminal and ground. If battery voltage is not present, repair open in Black/Yellow wire between solenoid valve and fuse No. 24.
  6. If battery voltage is present, reconnect vacuum gauge to vacuum hose No. 16. With engine running, connect terminal "B" of 4-pin connector of control box to battery positive terminal. While observing vacuum gauge, connect terminal "D" to negative battery terminal.
  7. If gauge does not read 8 in. Hg within one minute, turn ignition off. Inspect hoses No. 16 and 20 for leaks, restrictions and misrouting. If problem is found, repair as necessary. If hoses are okay, disconnect lower hose on EGR control solenoid valve, and connect a vacuum gauge.
  8. Start engine, and allow to idle. If 6-10 in. Hg is not present, replace Constant Vacuum Control (CVC) valve. If 6-10 in. Hg is present, replace EGR control solenoid valve. If gauge reads 8 in. Hg from previous step, reconnect 4-pin connector, and ensure ignition is off.
  9. Connect Test Harness (07GMJ-ML80100 ) to EGR lift sensor harness. Turn ignition on. Measure voltage between Red (positive) and Green (negative) wire terminals. If about 5 volts are not present, repair open in Yellow/White wire in connector C216 or Green wire in connector C318 between EGR valve and ECU terminal C13.
  10. If 5 volts are present, measure voltage between White (positive) and Green (negative) wire terminals. If about 1.2 volts are not present, replace EGR valve. Repair short in Yellow wire between terminal C8 and EGR lift sensor. If wire is okay, substitute a known good ECU. If proper voltage is present, replace ECU.
  11. If 1.2 volts are present, observe voltmeter, and apply 8 in. Hg to EGR valve. Repeat several times, fully releasing vacuum between checks. If maximum voltage is not 4 volts, replace EGR valve. If maximum voltage is 4 volts, ensure voltage consistently increases and decreases as vacuum increases and decreases.
  12. If voltage does not increase and decrease with vacuum, replace EGR valve. If vacuum increases and decreases with vacuum, reconnect hose No. 16 to EGR valve. Turn ignition off. Connect ECU test harness to ECU. Start engine, and allow to idle. Measure voltage between ECU terminals C8 (positive) and C12 (negative). If about 1.2 volts are not present, repair open in Green/Red wire between ECU terminal C8 and EGR lift sensor.
  13. If 1.2 volts are present, connect jumper between A8 and A18. If engine does not stall, repair open in Red wire between A8 and EGR control solenoid valve. If engine stalls, substitute a known good ECU. If condition goes away, replace ECU.
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