Engine oil temperature must be at a minimum of 120°F (50°C). Reconnect wiring to temperature sensor. Start engine and run it briefly at 2000 RPM. Release throttle.
If intake boot does not visibly contract, disconnect harness plug from deceleration fuel shutoff valve. Attach a voltmeter between harness terminals. Start engine and run it briefly at 2000 RPM. Release throttle.
If 12 volts are present and vacuum hose is okay, replace deceleration fuel shutoff valve. If 12 volts are not present, check operation and adjustment of throttle switch at idle. If okay, check throttle switch to ECU wiring for open.
NOTE: Deceleration fuel shutoff valve terminal identifications are located on connector.
If deceleration fuel shutoff valve still does not operate, use Adapter Cable (US 1112) and connect Green test lead to OXS system test connector (Blue/Black wire). Connect Dwell Meter (VW 1367) to vehicle. Set the "%" button on dwell meter. Disconnect harness connector from deceleration fuel shutoff valve. Using a jumper wire, connect harness side terminal No. 2 of deceleration fuel shutoff valve to ground.
If dwell meter does not indicate 40%, turn ignition off. Disconnect ECU harness connector. Check resistance in wire between ECU terminal No. 4 and deceleration fuel shutoff valve terminal No. 2. See Figure for ECU terminal identifications. Resistance should be less than .2 ohm. If not, check for open circuit in wire. If wire is okay, replace ECU.

NOTE: Throttle switch terminal identifications are located on connector.

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 Fuel Shutoff Check (Man. Trans. Only)