Inspection Procedure 23: 4L detection Switch System <Vehicles with 4WD, M/T and high power engine>

OPERATION

A 4L detection switch detects that a transmission is shifted into a 4L position.
An engine-ECU controls an engine speed to be 3, 000 r/min or less so that an excessive load cannot be applied to a drive train system due to a sudden start in a reverse gear position.

PROBABLE CAUSES

Failed 4L detection switch
Damaged harness (Open circuit between 4L detection switch and engine-ECU)
Damaged connector (Engine-ECU connector, 4L operation detection switch connector)
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check 4L detection switch itself

Check 4L detection switch itself (Refer to GROUP 22A - On-vehicle service - 4L detection switch continuity check ).

Q. Is the check result normal?

	Go to Step 2.

	Replace the 4L detection switch.

STEP 2. check harness between engine-ECU connector terminal 4L and 4L operation detection switch connector terminal.

Q. Is the check result normal?

	Replace the engine-ECU.

	Repair or replace the connector, or repair the damaged harness wire.