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 MANUALSAUDI199590 QUATTRO SPORT V6-2.8L (AAH)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTHROTTLE POSITION SENSORTESTING AND INSPECTIONCHECKING THROTTLE POSITION SIGNAL
1995 Audi 90 Quattro Sport V6-2.8L (AAH)
Checking Throttle Position Signal
1995 Audi 90 Quattro Sport V6-2.8L (AAH)SECTION Checking Throttle Position Signal
CHECKING THROTTLE POSITION SENSOR OUTPUT SIGNAL
NOTE: This signal is also used as a load signal for other control modules, e.g. Transmission Control Module (TCM). Carry out this test only if the output signal is actually used for applications other than the engine control module.
PROCEDURE
- Connect VAG 1598 test box with VAG 1598/11 adapter harness to the Engine Control Module (ECM). Connecting VAG 1598/31 Test Box
^ Connector D of wiring harness must be connected to ECM
- Connect US 1115 LED tester or equivalent between test box sockets 28 and 45.
- Switch ignition on.
^ LED must light up weakly in closed throttle position, and become brighter when accelerator pedal is depressed.
If LED still does not light up and does not become brighter:
- Disconnect connector -B- of ECM wiring harness from VAG 1598/11 adapter harness.
^ Connector B from VAG 1598/11 remains connected to ECM.
If LED does not light up or become brighter when accelerator pedal is depressed, the following malfunctions are possible:
- Faulty throttle position sensor (this means lack of input information for ECM).
^ Check TPS, replace if needed.
- Faulty Engine Control Module.
^ Replace ECM.
If LED lights up and becomes brighter when the accelerator pedal is depressed, the following malfunctions are possible:
^ Short circuit to Ground (GND) in wiring from ECM connector terminal 8 to TCM.
^ Malfunction in TCM (permanent short circuit to GND).
NOTE: This signal is also used as a load signal for other control modules, e.g. Transmission Control Module (TCM). Carry out this test only if the output signal is actually used for applications other than the engine control module.
PROCEDURE
- Connect VAG 1598 test box with VAG 1598/11 adapter harness to the Engine Control Module (ECM). Connecting VAG 1598/31 Test Box
^ Connector D of wiring harness must be connected to ECM
- Connect US 1115 LED tester or equivalent between test box sockets 28 and 45.
- Switch ignition on.
^ LED must light up weakly in closed throttle position, and become brighter when accelerator pedal is depressed.
If LED still does not light up and does not become brighter:
- Disconnect connector -B- of ECM wiring harness from VAG 1598/11 adapter harness.
^ Connector B from VAG 1598/11 remains connected to ECM.
If LED does not light up or become brighter when accelerator pedal is depressed, the following malfunctions are possible:
- Faulty throttle position sensor (this means lack of input information for ECM).
^ Check TPS, replace if needed.
- Faulty Engine Control Module.
^ Replace ECM.
If LED lights up and becomes brighter when the accelerator pedal is depressed, the following malfunctions are possible:
^ Short circuit to Ground (GND) in wiring from ECM connector terminal 8 to TCM.
^ Malfunction in TCM (permanent short circuit to GND).
RENDER: 1.0x
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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.