Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSVOLKSWAGEN1991GTI L4-1984CC 2.0L DOHC (9A)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSENGINE CONTROL MODULETESTING AND INSPECTIONCOMPONENT TESTS AND GENERAL DIAGNOSTICSDECELERATION FUEL SHUT-OFF
1991 Volkswagen GTI L4-1984cc 2.0L DOHC (9A)
Deceleration Fuel Shut-Off
1991 Volkswagen GTI L4-1984cc 2.0L DOHC (9A)SECTION Deceleration Fuel Shut-Off
Diaphragm Pressure Regulator Testing Connections:
NOTE: Engine oil temperature must be minimum of 140°F and the A/C system "OFF".
1. Connect an ammeter between the differential pressure regulator harness connector and the differential pressure regulator, using VOLKSWAGEN special tool #VW 1315A/1 or equivalent.
CAUTION: The small female terminals in the differential pressure regulator harness connector are easily damaged. If fabricating a test harness, use the appropriate male terminals to make connections with the harness connector.
Coolant Temperature Sensor:
2. Remove the harness connector from the coolant temperature sensor.
3. Switch the ignition "ON".
Differential pressure regulator current should be between 90 - 110 mA.
4. Start the engine and run at approx. 3000 RPM.
5. Close the throttle valve quickly.
6. Measure the differential pressure regulator current.
^ Differential Pressure Regulator current should change to a negative value briefly, and then return to its normal positive value.
If the correct measurement is not obtained check the throttle switch adjustment. Refer to ADJUSTMENT PROCEDURES.
If the throttle switch adjustment is correct check the CIS-E Motronic harness. Refer to SYSTEM ELECTRICAL TESTS.
If the harness is OK the CIS-E Motronic control unit may be defective.
7. Erase fault codes.
RENDER: 1.0x
NO RELATED
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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.