Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Inspection Procedure
For circuit wiring diagram, see Fig 1.
- Check the pattern select switch using the hand-held tester. Connect the hand-held tester to DLC3. See Figure. Check the pattern select switch using DATA LIST. If the results are OK, inspect the Engine Control Module (ECM). Check Electronic Control Module (ECM) connector for loose, damaged or corroded terminals and repair as necessary. If connector is okay, check ECM ground circuits. See appropriate wiring diagram in POWER DISTRIBUTION in WIRING DIAGRAMS article. Repair as necessary. If ground circuits are okay, replace ECM with a known-OK ECM and retest. If the results are not OK, go to the next step.
- Check the pattern select switch. See PATTERN SELECT SWITCH under COMPONENT TESTS under DIAGNOSIS - A-650E article under AUTOMATIC TRANSMISSION in TRANSAXLE/TRANSMISSION. If the results are OK, go to the next step. If the results are not OK, replace the pattern select switch.
- Check for short to power, short to ground and continuity in the wiring harness and connector between the pattern select switch and body ECU No. 1. If the results are OK, inspect the Engine Control Module (ECM). If the results are not OK, repair or replace the wiring harness or connector.
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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.
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