LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Honda >> 1994 >> Prelude VTEC >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Emission Systems & Sub-Systems >> Exhaust Gas RECIRCULATION (EGR) System >> D15Z1
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Exhaust Gas RECIRCULATION (EGR) System: D15Z1

  1. Start and idle engine. Disconnect vacuum hose from EGR valve, located to rear of distributor. Connect vacuum pump/gauge to hose. If vacuum exists, go to next step. If vacuum does not exist, go to step 4).
  2. Unplug 2-pin connector from control box. Control box is located at top center of firewall. If vacuum no longer exists, go to next step. If vacuum still exists, check EGR system vacuum hose routing.
  3. Turn ignition off. Unplug connector "A" from ECM. Check for short in Pink/Green wire (Orange/Blue wire after connector) between EGR control solenoid valve and ECM terminal A11. If wire is okay, replace ECM and retest system.
  4. Connect vacuum pump/gauge to EGR valve. Apply 8 in. Hg vacuum to EGR valve. If engine stalls or runs roughly, and EGR valve holds vacuum, go to next step. If engine operation remains same, or EGR valve does not hold vacuum, replace EGR valve.
  5. Turn ignition off. Unplug 2-pin connector from control box, located at top center of firewall. Turn ignition on. Measure voltage between harness connector Black/Yellow wire and ground. If battery voltage exists, go to next step. If battery voltage does not exist, repair Black/Yellow wire between EGR control solenoid valve and fuse panel. EGR control solenoid valve is located in control box.
  6. Reconnect vacuum pump/gauge to hose. Start and idle engine. Connect fused jumper wire between terminal "A" (Black/Yellow wire on mating harness connector) of control box connector and positive battery terminal.
  7. Observe vacuum gauge while connecting remaining control box terminal to ground. If gauge indicates about 8 in. Hg within one second, go to next step. If gauge indication is not as specified, go to step 13).
  8. Turn ignition off. Reconnect vehicle harness to control box. Unplug 3-pin connector from EGR valve. EGR valve is located behind distributor. Turn ignition on. Measure voltage between Yellow/White and Green/White wires at harness connector. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 15).
  9. Turn ignition off. Reconnect vehicle harness to EGR valve. Connect test harness. See Figure . Turn ignition on. Measure voltage between terminals D12 and D22 with no vacuum applied to EGR valve. Apply 8 in. Hg vacuum to EGR valve. Voltage should be about 1.2 volts with no vacuum applied and 4.3 volts with vacuum applied. If voltage is as specified, go to step 11).
  10. If voltage is not as specified, check for open or short circuit in White/Black wire between EGR valve and ECM terminal D12. If wire is okay, replace EGR valve.
  11. Observe voltmeter as vacuum is applied and released. If voltage increases and decreases smoothly, go to next step. If voltage change is not as specified, replace EGR valve.
  12. Reconnect hose to EGR valve. Start and idle engine. Connect jumper wire between terminals A11 and A26. If engine stalls or runs roughly, replace ECM and retest system. If engine does not stall or run roughly, repair open in Pink/Green or Orange/Blue wire between ECM terminal A11 and EGR control solenoid valve.
  13. Turn ignition off. Check vacuum hoses for leaks, restrictions and misrouting. If hoses are okay, go to next step. Repair as necessary.
  14. Disconnect lower hose from EGR control solenoid valve. EGR control solenoid valve is located in control box, at top center of firewall. Connect vacuum gauge/pump to hose. Start and idle engine. If gauge indicates 6-10 in. Hg vacuum, replace EGR control solenoid valve. If vacuum is not as specified, replace EGR vacuum control valve, located in control box.
  15. Measure voltage between Yellow/White wire and body ground. If voltage is not about 5 volts, go to next step. If voltage is about 5 volts, repair open in Green/White wire between ECM terminal D22 and EGR valve.
  16. Turn ignition off. Connect test harness. See Figure . Turn ignition on. Measure voltage between terminals D20 and D22. If voltage is about 5 volts, repair open in Yellow/White wire between EGR valve and ECM terminal D20. If voltage is not about 5 volts, replace ECM and retest system.
scientia non olet · About LEMON Manuals