P0098 on Audi: Causes, Symptoms and Fix Cost

The Quick Answer above is the generic definition. What follows is the model-specific detail for the Audi models that log P0098.

Beyond the generic causes listed on the main P0098 page, these are the patterns noted for Audi models:

Follow these steps to pinpoint the root cause of P0098:

1. With the engine off after a night parked, read both intake air temperature values in live data. They should agree within a few degrees. If sensor 2 sits at its minimum of about -40 C while sensor 1 shows the real ambient temperature, the circuit is open rather than genuinely cold
2. Find the sensor. On turbocharged and supercharged engines it is normally in the charge air pipe between the intercooler and the throttle body, and on many cars it is built into the boost pressure sensor in that same pipe. Some engines instead place it in the intake manifold
3. Unclip the connector, look for corrosion, spread or backed out pins and water inside, then clean it and push it back on until it clicks. Wiggle the plug and the first stretch of harness while watching the live reading, since a value that jumps back to a sensible number points at the connector
4. Work out which pin is which before you probe anything. A standalone temperature sensor has two pins, one signal and one sensor ground. A combined charge air pressure and temperature sensor has four, carrying a 5 volt reference, a sensor ground, a pressure signal and a temperature signal, so on those you have to identify them first. Take the pinout from a wiring diagram for your exact engine, and if you cannot tell the pins apart with confidence, stop here and let a workshop do the next two steps. Then turn the ignition on with the engine off, unplug the connector and measure the voltage between the temperature signal pin and the sensor ground pin. Around 5 volts confirms that the supply and the sensor ground both reach the plug. No voltage means the supply or the ground side is open before you even get to the sensor
5. This is the step that separates a bad sensor from a broken wire, and it is the one step where the wrong pin does real damage. Leave the connector unplugged with the ignition on and bridge the temperature signal pin to the sensor ground pin only, using a short jumper wire. Never bridge the 5 volt reference pin to ground: the ECU feeds that same reference to other sensors, and shorting it can turn one fault code into a dashboard full of them. If the live reading jumps to its maximum, roughly 120 to 150 C, then the wiring and the ECU are fine and the sensor itself is faulty. If the reading stays at -40 C, the sensor is innocent and the fault is in the harness or at the ECU
6. Confirm the verdict. Measure the sensor across its terminals with a multimeter, where a healthy NTC reads roughly 2,000 to 3,000 ohms at 20 C and an infinite reading proves it is open internally. If the jumper test pointed at the harness instead, check continuity of the signal and sensor ground wires back to the ECU connector and repair the break

Estimated repair costs for P0098 in EUR, compiled across makes. Expect Audi parts and labour towards the upper end of each range.

These codes are often seen alongside P0098 or point to related issues, on any make: