Test D11 - "Check Engine" Light/Message-Malfunction Indicator

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: fuses, bulb, or socket. This circuit test checks STO-MIL circuit and ECA.

Fig 1: "CHECK ENGINE" Light (Malfunction Indicator) Circuit

NOTE: All service codes, except a code 11 (pass), must be cleared before continuing.

Light Always On: Checking Short to Ground - If vehicle will not start, go to TEST A1 , step 1). Verify presence of KOEO SELF-TEST code 11. If not, repeat QUICK TEST . Turn key off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Connect DVOM between Test Pins No. 17 (No. 53 on 1.9L MPFI) and No. 40 at the breakout box. If reading is greater than 5 ohms, replace ECA. If reading is less than 5 ohms, repair short to ground in harness from Test Pin No. 17 (No. 53 on 1.9L MPFI) to SELF-TEST connector or to "CHECK ENGINE" light.
Light Never On: Check Continuity of STO/MIL Circuit - If vehicle will not start, go to TEST A1 , step 1). Verify presence of KOEO SELF-TEST code 11. If not, repeat QUICK TEST . Turn key off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between Test Pin No. 17 (No. 53 on 1.9L MPFI) and STO at SELF-TEST connector. Also measure resistance between Test Pin No. 17 and "CHECK ENGINE" light. If both readings are less than 5 ohms, go to next step. If not, repair open circuit in wiring harness.
Checking For Power to "CHECK ENGINE" Light Bulb - If power exists at bulb, replace bulb or socket and go to next step. If no power exists at socket, check fuse and input circuit, and then go to next step.
Confirming Circuit Repair - Remove breakout box and reconnect ECA to harness. Turn key to "RUN" position. See if "CHECK ENGINE" light is on. If light is on, malfunction indicator system is okay. If light does not come on, replace ECA.
"CHECK ENGINE"/"CHECK DCL" Message Displayed - If vehicle does not start, go to TEST A1 , step 1). Perform KEY ON/ENGINE OFF (KOEO) SELF-TEST . If result is 11-10-11 (pass codes), malfunction is in Message Center Unit. If 11-10-11 is not displayed, go to QUICK TEST .