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.
1999 Audi A4 Base, 1.8 B, AutomaticFACTORY OEM SERVICE PROCEDURE
Engine Controls - Sensor Operating Range Charts: Introduction
Sensor operating range information can help determine if a sensor is out of calibration. An out-of-calibration sensor may not set a trouble code, but it may cause driveability problems.
NOTE:
Unless stated otherwise in test procedure, perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance.
ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE
| Temperature | Ohms |
|---|---|
| 86°F (30°C) | 1500-2000 |
| 176°F (80°C) | 275-375 |
HEATED OXYGEN SENSOR (HO2S) RESISTANCE
| Terminals No. | Ohms |
|---|---|
| 1 & 2 | 0.0-19.9 |
HEATED OXYGEN SENSOR (HO2S) VOLTAGE
| Condition | Volts |
|---|---|
| Lean | Approx. 0.2 |
| Rich | Approx. 0.7 |
INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE
| Terminals | Ohms | |
|---|---|---|
| Measure Between Sensor Terminals | ||
| 1.8L Turbo | Approx. 1600-2800 | |
| 2.8L | Approx. 1500-3500 | |
KNOCK SENSOR RESISTANCE (1.8L TURBO)
| Terminal No. | Ohms |
|---|---|
| 1 & 2 | Infinity |
| 1 & 3 | Infinity |
| 2 & 3 | Infinity |
Factory Service Tools
Use the Manual With the Right Hardware
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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.