Diagnosis & Repair
WARNING: This page is about a different car, the 2002 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.
- Check for spark at misfiring cylinder. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If spark exists, go to next step. If spark does not exist, go to step 4.
- Check for open or short in IGF and IGT circuits between suspect ignition coil/ignitor and ECM. See WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
- Disconnect suspect ignition coil/ignitor harness connector. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe at ECM harness connector and measure voltage between ground and following terminal:
- For cylinders No. 1, 4, 6 or 7, measure at terminal No. 27 (Black/White wire) at ECM harness connector E6.
- For cylinders No. 2, 3, 5 or 8, measure at terminal No. 28 (Black/Red wire) at ECM harness connector E6.
See Figure. If voltage is 4.5-5.5 volts, replace suspect ignition coil/ignitor. If voltage is not 4.5-5.5 volts, replace ECM.
- Backprobing at ECM harness connector E6, check for open or short in IGT circuit between appropriate ignition coil/ignitor terminal No. 3 and ECM harness connector terminal. See IDENTIFYING IGT CIRCUIT ECM E6 CONNECTOR TERMINALS table. See WIRING DIAGRAMS
article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.IDENTIFYING IGT CIRCUIT ECM E6 CONNECTOR TERMINALS
Ignition Coil/Ignitor No. Circuit (Terminal No.) Wire Color 1 IGT1 (11) Black 2 IGT2 (12) Red 3 IGT3 (13) Blue 4 IGT4 (14) Green 5 IGT5 (15) Yellow 6 IGT6 (16) Black/Yellow 7 IGT7 (25) Black/Blue 8 IGT8 (26) Blue/Black - Access ECM behind glove box. Using DVOM, backprobe ECM harness connector and measure voltage between ground and appropriate IGT circuit terminal at ECM harness connector E6 while cranking engine. See IDENTIFYING IGT CIRCUIT ECM E6 CONNECTOR TERMINALS table. See Figure. If voltage is .1-4.5 volts, go to next step. If voltage is not .1-4.5 volts, replace ECM.
- Disconnect appropriate ignition coil/ignitor harness connector. Using DVOM, backprobe ECM harness connector and measure voltage between ground and appropriate IGT circuit terminal at ECM harness connector E6 while cranking engine. If voltage is .1-4.5 volts, go to next step. If voltage is not .1-4.5 volts, replace ECM.
- Measure voltage between ground and terminal No. 1 (Black/Red wire) at appropriate ignition coil/ignitor harness connector in both ignition ON and START positions. See Fig 1. If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check and repair ignition coil/ignitor No. 1 power source circuit. See WIRING DIAGRAMS article.
- Check for open or short in wiring between ground and ignition coil/ignitor No. 1. See WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
- Check EFI main relay. See MOTORS & RELAYS in SYSTEM & COMPONENT TESTING article. If problem exists, replace EFI main relay. If problem does not exist, replace ignition coil/ignitor No. 1.