1993 Acura Legend Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Code 12: EGR System

  1. Turn ignition off. Remove ACG (No. 15, 7.5-amp) from fuse in underdash fuse box for 10 seconds to reset ECM. Warm engine until cooling fan comes on. Road test vehicle about 10 minutes, keeping engine speed about 1700-2500 RPM. Check for fault codes. If Code 12 is not present, problem is intermittent. Check for poor connections at ECM, EGR valve, control box and shock tower wiring harness connectors.
  2. Test drive vehicle and retest. If Code 12 is present, start engine. Disconnect No. 11 hose from EGR valve. See Fig 1 . Start engine. Connect vacuum gauge to hose. If no vacuum is present, go to step 4. If vacuum is present, disconnect 4-pin connector from control box, located on right side of firewall. Check vacuum again on No. 11 hose. If vacuum is present, check vacuum hose routing. If routing is okay, replace EGR control solenoid valve.
    Fig 1: Identifying EGR No. 11 Hose
    G92G26217Courtesy of AMERICAN HONDA MOTOR CO., INC.
  3. If vacuum is not present, turn ignition off. Remove connector "A" from ECM. Using an ohmmeter, check for continuity between White wire terminal of 4-pin connector and ground. If continuity is present, repair short in White wire between EGR control solenoid valve and ECM connector terminal A11. If continuity is not present, replace ECM and retest.
  4. If vacuum was not present during first vacuum test in step 2, install vacuum pump on EGR valve. With engine idling, apply 8 in. Hg to EGR valve. If engine does not stall or run rough or EGR valve does not hold vacuum, replace EGR valve.
  5. If engine stalls or runs rough and EGR valve holds vacuum, disconnect 4-pin connector from control box. Measure voltage between Black/Yellow wire terminal and body ground. If battery voltage is not present, repair open in Black/Yellow wire between solenoid valve and FUEL PUMP fuse (No. 22, 20-amp) in underdash fuse box.
  6. If battery voltage is present, install "T" fitting into No. 11 hose. Attach vacuum gauge to "T" fitting. Start engine, and allow it to idle. Connect battery voltage to terminal "A" of control box connector. See Fig 2 . While observing vacuum gauge, connect terminal "B" to negative battery terminal.
  7. If gauge reads 6 in. Hg within one second, go to step 9. If gauge does not read 6 in. Hg within one second, turn ignition off. Inspect hoses for leaks, restrictions and misrouting. Repair as necessary. If hoses are okay, disconnect lower hose on EGR control solenoid valve.
  8. Connect vacuum gauge to hose. See Figure . Start engine, and allow it to idle. If 4.8-6.8 in. Hg is not present, replace Constant Vacuum Control (CVC) valve. See Fig 3 . If 4.8-6.8 in. Hg is present, replace EGR control solenoid valve. See Fig 3 .
    Fig 2: Identifying Control Box Connector Terminals
    G91B16288Courtesy of AMERICAN HONDA MOTOR CO., INC.
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

Shop Manual-Ready ToolsCompare Repair QuoteQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

Rather have a pro handle this?

A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.

Comes to youSame-day available12-month warranty
Get a Free Quote

No obligation. See pricing before you book.