NOTE: On vehicles with complaints of engine surging with cruise control engaged, check cruise control input to ECU.

Engine should be at operating temperature. Increase engine speed to 2500 RPM. Maintain constant RPM and actuate micro-switch manually. If engine RPM fluctuates, check adjustment of slotted lever. If there is no surge, go to next step.
Using multimeter, check resistance of throttle valve microswitch. Resistance should be zero ohms. If free travel on lever is canceled, resistance should read infinity. If resistance is not correct, replace microswitch. If resistance is correct, go to next step.
Connect meter adapter cable to differential pressure regulator. Set multimeter on mA scale. Increase engine speed to 2500 RPM and release throttle. Current reading should be at least 45 mA until restarting speed of 900 RPM is reached. Direction of current is negative to positive. If current is correct, test is complete. If current is not correct, go to next step.
With engine running, check RPM signal (TD) on Green/Yellow wire at ECU terminal No. 25. Set multimeter to volt scale. Reading should be 8.5 volts. If not, repair wiring circuit. If voltage is correct, go to next step.
Test wiring between ECU plug and differential pressure regulator for continuity. Resistance reading should be zero ohms. If not, repair wiring circuit. If reading is correct, replace ECU. Test is complete.

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.

Safety Warning

Deceleration Shut-Off: Notes