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7 Simple Changes That'll Make A Huge Difference In Your Audi G28
How to Replace an Audi G28 Engine Speed Sensor

Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. This sensor is situated near the transmission's edge just above the flywheel gear. It transmits a signal the ECU via a grey wire (T55/49) and then to the tachometer within 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 the grey wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends an alert to the G5 Tachometer located in the instrument cluster.

The sensor is used to correlate the G40 Camshaft position Sensor. The ecu has to be aware of when the crankshaft has reached TDC, and the location of the camshaft to trigger the spark and injectors.

If this sensor fails to function, the ECU will display an error code P00160. This means that the Crank Shaft is not in alignment with the Intake Camshaft. It could also indicate an issue with the chain or a jumpy chain link in the upper chain. The code will not appear without the additional information supplied by other sensors (G4 or G40).

It is a little tricky to test because 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 fully functional, it should read about 1000 ohms. If you are having problems with this component, look for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll, i experienced massive power loss like the engine is out of gas or the injectors are not firing any more. I pulled out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was dry. I placed a tissue over each injector hole, and when i turn the engine on without sparks, the 3 that have gazoline pop right out. The 4th one remains shut. I checked the ground connection on ECU pins 14/55,30/55 and 48/55 I get 0ohm. Therefore, i think the issue is in another place.

I also tried to reset PID but without success. The car will start if the G28 is disconnected and runs fine when it is connected however it has intermittent misfire issues at higher RPM. The coolant temperature sensor (G62) shows the wrong temp value -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is zero.

I'm not certain what to do, as i feel i have pretty much completely ruled out all other possibilities. But i am afraid i might have missed something. Please let me know should you have any suggestions! TIA!

3. audi keys www.thekeylab.co.uk of the g28 gets a signal from the RPM sensor. The GM-style sensor is the same as the G4 and they both work in the 80 100, 200, UrS and RS2 cars so you can easily find one at a wrecking yard or from a parts store. Testing them is easy to do - just put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's end). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that must be aware of the speed and position of the crankshaft to make decisions about timing of the fuel injectors, etc. In order to do this it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go bad you will get codes on the diagnostic scanner which could cause engine shut down.

Some of the signs of a failed G28 sensor are an inaccurate rev counter for the gearbox the gears are shifting faster than normal and/or a misfire when you're in gear. If you have any of these issues it is likely your sensor is failing and should be replaced. They are cheap and easy-to-find, especially when they're a Bosch unit like ours. You can also choose the GM version of this component is also a good option.


5. Tachometer

A malfunctioning engine sensor can cause a variety of issues in your vehicle. It is a crucial part of your Audi's transmission, since it relays information to the ECU about how fast or slow the car's crankshaft is turning. When this sensor fails, it could cause problems for the transmission, as well as the other car's components.

The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It sends a signal via an uncolored wire to the ECU pin T55/49. The ECU uses this signal to control the amount of fuel and boost, and also timig. It also sends it to the G5 Tachometer located in the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. There should be the resistance to be around 1000 ohms between these points. This is a standard part that is found across the Audi 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best ones could be available in wrecking yards.