Lexus ECU/ECM

Lexus ECU/ECM Post-Repair Troubleshooting Guide

Important: Use this guide if you reinstalled your repaired Lexus ECU/ECM and the problem is still happening.
Important: Please do not open/disassemble the module. This can damage the unit and may void warranty coverage.

Step 1: Battery voltage + code reset

• Fully charge the battery (low voltage can trigger false codes)
• Clear codes, then key OFF 60 seconds and restart
• Re-scan and write down which codes return first

Step 2: ECU connectors (most common issue)

• Key OFF, unplug ECU connectors
• Inspect for bent pins, pushed-out pins, corrosion, moisture, or damaged seals
• Re-seat connectors fully until the locks click/fully latch

Step 3: Check power/ground and ECU fuses

• Verify ECU/EFI/IGN fuses and relays in the underhood fuse box
• Confirm grounds are clean/tight (battery negative to body, engine ground straps)

Step 4: If you have shift/solenoid codes (P0750/P0753/P0755/P0758/P0761)

• These are typically transmission-side or harness issues, not ECU-only
• Check transmission connector for oil intrusion, corrosion, or loose pins
• Inspect the engine-to-transmission harness for rubbing/heat damage
• Verify ATF level/condition (low/dirty fluid can cause solenoid performance codes)

Step 5: If the car goes into limp mode or shifts harsh

• Check for weak battery/charging system (alternator output and grounds)
• Inspect/clean the main engine grounds and fuse box power feeds
• Confirm no recent wiring/engine work caused a pinched or unplugged connector

Step 6: If codes return immediately after clearing

• A local shop should verify solenoid resistance at the transmission connector and confirm wiring continuity from ECU to trans
• Multiple related solenoid codes often point to harness/connector/valve body faults

If the issue started right after wiring, sensor, fuse, relay, or transmission work, re-check the exact areas serviced first. If the problem continues, contact UpFix with your VIN and your full code list.