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.
Testing
Throttle Angle Output Signal Checking: Testing — 1994 Audi S4 Service Manual & Component Testing >> Engine Sensors & Switches >> Throttle Angle Output Signal Checking >> Testing Throttle Angle Output Signal Checking: Testing Connect (VAG 1598) test box, using (VAG 1598/5) adapter cable to ECM. See CONNECTING VAG 1598 TEST BOX. Connect (US 1115) LED tester between ground terminal No. 19, and terminal No. 54. Start engine and let idle. LED tester must light up dimly. Apply accelerator pedal. LED tester light must become brighter. If LED tester does NOT light up or is NOT brighter when applying accelerator pedal. Check for malfunctioning Throttle Position (TP) sensor. See THROTTLE POSITION SENSOR. If TP sensor Okay: Replace ECM. After replacement of ECM, see ECM IDENTIFICATION and ECM CODING under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS article. If LED tester lights up and is brighter (when applying accelerator pedal): Check for short to ground between ECM terminal No. 54 and Transmission Control Module (TCM). See WIRING DIAGRAMS. Check for malfunction in TCM - constant short to ground.
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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.