DTC P18A7-62: Gear Shift Control Module "A"/"B" IGCT Signal Compare Failure [10/2022 - ]: Procedure
WARNING: This page is about a different car, the 2025 Lexus RX 450h+, 2025 Lexus RX 350h, 2024 Lexus RX 450h+, 2024 Lexus RX 350h, and 2023 Lexus RX 350h. However, it is still accessible from the selected car via links, so may be relevant.
- CHECK HARNESS AND CONNECTOR (IGCT TERMINAL VOLTAGE)
Pre-procedure1
- Disconnect the B56 shift control actuator assembly (shift actuator ECU) connector.
- Connect the cable to the negative (-) auxiliary battery terminal.
- Turn the ignition switch to ON.
- Measure the voltage according to the value(s) in the table below.
Standard Voltage
Tester Connection Switch Condition Specified Condition Result B56-5 (IGC1) - Body ground Ignition switch ON 11 to 14 V V Result
Proceed to OK NG
Post-procedure1
- Turn the ignition switch off.
- Disconnect the cable from the negative (-) auxiliary battery terminal.
- Reconnect the shift control actuator assembly (shift actuator ECU) connector.
Result:
OK
REPLACE SHIFT CONTROL ACTUATOR ASSEMBLY (SHIFT ACTUATOR ECU). Refer to REMOVAL [10/2022 - 08/2023] , or refer to REMOVAL [08/2023 - ]
Result:
NG
See step 2
- INSPECT IGCT NO. 1 RELAY
Pre-procedure1
- Remove the IGCT NO. 1 relay from the No. 1 engine room relay block and No. 1 junction block assembly.
- Measure the resistance according to the value(s) in the table below.
*1 IGCT NO. 1 Relay Standard Resistance
Tester Connection Condition Specified Condition Result 3 - 5 Auxiliary battery voltage not applied between terminals 1 and 2 10 kΩ or higher kΩ 3 - 5 Auxiliary battery voltage applied between terminals 1 and 2 Below 1 Ω Ω Result
Proceed to OK NG
Post-procedure1
- Install the IGCT NO. 1 relay to the No. 1 engine room relay block and No. 1 junction block assembly.
Result:
OK
REPAIR OR REPLACE HARNESS OR CONNECTOR (IGCT POWER SUPPLY CIRCUIT)
Result:
NG
REPLACE IGCT NO. 1 RELAY