Code 18: Ignition Timing Adjuster
NOTE:
For wiring diagrams, see WIRING DIAGRAMS
article. For vacuum diagrams, see VACUUM DIAGRAMS
article.
- Turn ignition off. Remove alternator sense fuse in under-hood relay box for 10 seconds to reset ECU. Turn ignition on. Verify if CHECK ENGINE and Red LED lights are on. If not, problem is intermittent. Check for poor connections or loose wires at ignition timing adjuster connector. See Fig 1 .
- If CHECK ENGINE light is on and Red LED indicates Code 18, turn ignition off. Disconnect ignition timing adjuster 4-pin connector with only 3 wires at right side of firewall. See Fig 1 . Measure resistance between Yellow/White and Green/White wire terminals of ignition timing adjuster.
- Resistance should be 3000-6000 ohms. If resistance is as specified, go to step 4). If not, replace ignition timing adjuster.
- If resistance is within specification, measure and record resistance between Brown and Yellow/White wire terminals on timing adjuster side of harness. Measure and record resistance between Brown and Green/White wire terminals on same side of connector. Add the 2 resistance values together. If the total of the resistance values is not 3500-6500 ohms, replace ignition timing adjuster.
- If resistance values fall within 3500-6500 ohms, turn ignition on. Measure voltage between Yellow/White (positive) and Green/White (negative) wire terminals on harness side of connector. If voltage is about 5 volts, go to step 7). If voltage reading is not about 5 volts, measure voltage between ground and Yellow/White wire terminal. If voltage reading is about 5 volts, repair open in Green/White wire between ECU terminal C14 and ignition timing adjuster connector. If voltage is not 5 volts, go to step 6).
- Turn ignition off. Connect ECU test harness between ECU and ECU connector. Turn ignition on. Measure voltage between ECU terminals C13 (positive) and C14 (negative). See Figure . If about 5 volts is present, repair open in Yellow/White wire between ECU terminal C13 and ignition timing adjuster. If not, substitute a known good ECU and recheck. If specified voltage is now available, replace original ECU.
- If voltage reading between Yellow/White and Green/White (negative) wire terminals in step 5) was about 5 volts, turn ignition off. Reconnect ignition timing adjuster connector. Connect ECU test harness between ECU and ECU connector. Turn ignition on. Measure voltage between ECU terminals B18 (positive) and C14 (negative). If voltage is not .5-4.5 volts, repair open or short in Brown wire between ECU terminal B18 and ignition timing adjuster.
- If voltage reads .5-4.5 volts, substitute a known good ECU and recheck. If condition goes away, replace original ECU.