How to Replace an Audi G28 Engine Speed Sensor

In this video, Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is located at the edge of transmission just above the flywheel gear. It sends a signal to the ECU via the grey wire (T55/49) which is then sent to the tachometer in the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through a grey wire. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an indicator to the G5 Tachometer located in the instrument cluster.

The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and the location of the camshaft so it can start spark and injectors in the right way.

If this sensor fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is not in line with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumpy chain link in the upper timing chain. The code will not appear without the additional information provided by other sensors (G4 or G40).

It's a bit tricky to test since there are different pins on the connector and each has its own functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. When the sensor is functional, it should read about 1000 ohms. If you're having issues with this sensor, look for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, when accelerating from highway paytoll at maximum speed, i noticed a huge reduction in power. It was as if the engine was running out of gas. Or, my injectors weren't firing. I pulled out the spark plugs this morning, 3 were soaked in gasoline, and the fourth was unclean. I placed a tissue over each injector hole, and when I start the engine without sparks, the 3 with gazoline jump out. The 4th one remains shut. I checked the ground connection of ECU pins 14,30 and 48/55. I found zero ohm. Therefore, i think the issue is somewhere else.

I also tried to reset the PID with no success. The car can start if the G28 is unplugged and it runs perfectly when it is connected but it still has the intermittent misfire issue at higher RPM. The coolant sensor (G62), even when unplugged, still shows temperatures of -49c. I also noticed that the gauge for oil pressure in the cockpit shows 2 bar when the actual pressure is 0.0 if i crank up the engine.

I'm not sure what to do. I believe that I've all other possibilities out. But i am afraid I may have missed something. If anyone has any ideas please let me know! TIA!

3. audi a4 key replacement of the g28 receives a signal from the RPM sensor. The GM-style transmitter is similar to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find a spare in a wrecking shop or parts store. It is simple to test them - simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines needs to be aware of the position and speed the crankshaft in order to make a decision about timing of fuel injectors, etc. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go badly, you will see codes on the diagnostic scanner which can cause the engine to shut down.


Some of the symptoms of a failed G28 sensor are an inaccurate gearbox rev counter the gears are shifting faster than normal, and/or a misfire when in gear. If you experience any of these issues it is likely your sensor is failing and needs replacing. They are cheap and easy-to-find particularly if they're a Bosch sensor like ours. Alternatively, GM's version of this part is a good option.

5. Tachometer

A failing engine sensor could cause a number of problems in your car. It's an essential component of your Audi's transmission, because it communicates to the ECU about how the car's crankshaft is spinning. This sensor could cause the transmission to fail and other components of the car to be affected.

The G5 engine sensor is located at the edge of the transmission, over the flywheel ring. It sends signals via gray wire to ECU pin T55/49. The ECU uses this signal to regulate the amount of fuel and boost, and also to timigrate. It also transmits it to the G5 Tachometer inside the instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. Additionally, you can check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 and pin T26a/12. There should be a resistance of approximately 1000 ohms between these two points. This is a typical part across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good ones could be available in wrecking yards.