Diagnosis & Repair
WARNING: This page is about a different car, the 2003 Toyota 4Runner. However, it is still accessible from the selected car via links, so may be relevant.
- Remove spark plug for misfiring cylinder. Ensure no carbon deposits exist, spark plug is not fouled and spark plug gap is .043" (1.10 mm). Check ignition system by performing spark test on misfiring cylinder. Disconnect each fuel injector connector while performing spark test. See SPARK TEST under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. If ignition system operates properly and spark exists, go to next step. If ignition system does not operate properly and spark does not exist, go to step 4.
- Turn ignition off. Remove glove box for access to ECM with connectors. See Figure. Disconnect all 8 ignition coil 4-pin connectors and ECM 34-pin connector E4. See Figure & Figure
. Check continuity between ignition coil 4-pin connector terminal and ECM 34-pin connector E4 terminals. See IDENTIFYING ECM (IGF) TO IGNITION COILS TERMINALS for appropriate ignition coil and ECM 34-pin connector E4 terminal selections. Continuity should exist. Then, check continuity between body ground and ECM 34-pin connector E4 terminals No. 23 (Red/White wire) and No. 24 (Red/Yellow wire) individually. There should be no continuity. If continuity is as specified, go to next step. If continuity is not as specified, repair or replace wires and/or connectors as necessary.IDENTIFYING ECM (IGF) TO IGNITION COILS TERMINALS
Ignition Coil No. (1) (3) ECM 34-Pin Connector E4 Terminal No. Wire Color 1 (2) No. 24 Red/Yellow 2 (2) No. 23 Red/White 3 (2) No. 23 Red/White 4 (2) No. 24 Red/Yellow 5 (2) No. 23 Red/White 6 (2) No. 24 Red/Yellow 7 (2) No. 24 Red/Yellow 8 (2) No. 23 Red/White (1) Ignition coil No. 1 is front ignition coil on passenger's side of engine. Ignition coil No. 2 is front ignition coil on driver's side of engine. Ignition coils No. 1, 3, 5 and 7 are on passenger's side of engine. Ignition coils No. 2, 4, 6 and 8 are on driver's side of engine. (2) For all continuity checks, use ignition coil 4-pin connector terminal No. 2. (3) For ECM electrical connector terminal identification, see Figure. - Reconnect ECM 34-pin connector E4. Turn ignition on. Backprobing, measure voltage between ECM 34-pin connector E4 terminal No. 24 (+) (IGF1) and ECM 32-pin connector E6 terminal No. 1 (-) (Red/Yellow wire). Then, measure voltage between ECM 34-pin connector E4 terminal No. 23 (+) (IGF2) and ECM 32-pin connector E6 terminal No. 1 (-) (Red/White wire). Voltage should be 4.5-5.5 volts at both checks. If voltage is not as specified, replace ECM. If voltage is as specified, replace ignition coil(s).
- Remove glove box to gain access to ECM connectors. See Figure. Disconnect all 8 ignition coil 4-pin connectors and ECM 34-pin connector E4. See Figure and Figure
. Check continuity between ignition coil 4-pin connector terminal and ECM 34-pin connector E4 terminals. See IDENTIFYING ECM (IGT) TO IGNITION COILS TERMINALS for appropriate ignition coil and ECM 34-pin connector E4 terminal selections. Continuity should exist. Then, check continuity between body ground and each ignition coil 4-pin connector terminal No. 3, individually. There should be no continuity. If continuity is as specified, go to next step. If continuity is not as specified, repair or replace harness and/or connectors as necessary.IDENTIFYING ECM (IGT) TO IGNITION COILS TERMINALS
Ignition Coil No. (1) (2) ECM 34-Pin Connector E4 Terminal No. Wire Color 1 (3) No. 9 Light Green 2 (3) No. 8 Light Green/Black 3 (3) No. 25 Blue/White 4 (3) No. 11 Blue/Yellow 5 (3) No. 12 Black/Blue 6 (3) No. 26 Green 7 (3) No. 13 Green/White 8 (3) No. 10 Green/Black (1) Ignition coil No. 1 is front ignition coil on passenger's side of engine. Ignition coil No. 2 is front ignition coil on driver's side of engine. Ignition coils No. 1, 3, 5 and 7 are on passenger's side of engine. Ignition coils No. 2, 4, 6 and 8 are on driver's side of engine. (2) For ECM electrical connector terminal identification, see Figure. (3) For all continuity checks, use ignition coil 4-pin connector terminal No. 3. - Reconnect ECM 34-pin connector E4. Turn ignition on. Backprobing, measure voltage while engine is being cranked, between ECM 34-pin connector E4 (IGT+) terminals and ECM 32-pin connector E6 terminal No. 1 (-) (Red/Yellow wire). See IDENTIFYING ECM (IGT) TO IGNITION COILS TERMINALS for ECM terminal selections. Voltage should be more than 0.1 volt and less than 4.5 volts at all 8 checks. If voltage is not as specified, replace ECM. If voltage is as specified, go to next step.NOTE: During cranking or idling, check the waveform using an oscilloscope at the same terminals checked above. ECM IGT and IGF signal waveform patterns should be properly displayed. See Fig 1.
- Ignition still on, measure voltage between ground and suspect ignition coil 4-pin connector terminal No. 1 (Black/Red wire). See Figure. Voltage should be between 9-14 volts. If voltage is as specified, replace ignition coil(s). If voltage is not as specified, go to next step.
- Turn ignition off. Disconnect ignition switch 8-pin connector. Check continuity between suspect ignition coil 4-pin connector terminal No. 1 (Black/Red wire) and ignition switch 8-pin connector terminal No. 6 (IG2). Continuity should exist. Then, check continuity between body ground and ignition switch 8-pin connector terminal No. 6 (IG2). Continuity should not exist. If continuity is as specified, replace ignition coil(s). If continuity is not as specified, repair or replace harness wire and/or connector as necessary.