This Is The Ugly Truth About Audi G28

How to Replace an Audi A5 Key Fob G28 Engine Speed Sensor

Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is located near the edges of the transmission above the flywheel ring gear. It transmits a signal the ECU via the grey wire (T55/49) and then 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 via a grey wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends an indication to the G5 tachometer inside the instrument cluster.

The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can start spark and injectors accordingly.

If this sensor fails, the ECU will display the P00160 error, which means the Crank Shaft and Intake Camshaft are out of sync and possibly indicating the chain stretching or a jump link on the upper timing chain. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).

Testing is a bit challenging as there are two different connector pins and they serve different purposes however the best method of testing it is to measure the resistance between the sensor and the ECU. It should read approximately 1000 ohms if the sensor is in full operation. Look for signs of coolant or oil in the connector bay if you are experiencing problems with this part.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll i had massive power loss like the engine is out of gas or injectors are not firing anymore. I took out the spark plugs this morning, 3 were soaked with gasoline and the 4th was dry. I put tissue over each hole in the injector and when i turn the engine on without sparks, the ones that have gazoline pop right out. The 4th one remains closed. I tried to test the ground connections of ECU pins 14,30, and 48/55. I found 0ohm. I think the issue is somewhere else.

I also tried to reset PID but without success. The car is able to start when the G28 is unplugged and it runs perfectly when it is connected however it is experiencing intermittent misfires at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value -49c, even if I unplug it. Also i noticed that the gauge for oil pressure in the cockpit is showing 2 bar while the actual pressure is 0.0 when i rev the engine.

I'm not sure what to do, i feel i have pretty much eliminated everything else. But i am afraid i might have missed something. Let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style sensor is the same as the G4 and both function in the 80 100, 200, UrS and RS2 cars so you can easily find one at a wrecking yard or at a parts store. It is simple to test them by putting your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black end of the connector). They should be infinite Ohms.

4. ECU

Our 20vt turbo (3B, AAN, shop ABY and Audi A1 Keys ADU) engines are equipped with an ECU that needs to be aware of the speed and position of the crankshaft in order to make decisions about timing of the fuel injector, for example. To do this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these, the diagnostic scanner will show codes that could lead to the engine shutting down.

The signs of a failing G28 sensor are an inaccurate rev counter in the gearbox the gears are shifting faster than normal and/or misfiring when you are in gear. It is probable that your sensor is failing and requires to be replaced if you encounter any of these signs. The good thing is that they are very affordable and readily available particularly when you're looking at an Bosch sensor, like ours. Alternatively, GM's version of this part would be an excellent choice.

5. Tachometer

A faulty engine speed sensor could be a cause for numerous issues in your vehicle. It's an essential component of your audi car key's transmission, as it sends information to the ECU about how the car's crankshaft is turning. If the sensor fails, it will cause problems for the transmission as well as the other car's components.

The G5 engine speed sensor is situated on the edge of the transmission just above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU utilizes this signal to control the flow of fuel and boost and also to timigrate. It also relays it to the G5 Tachometer inside the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see approximately 1000 ohms of resistance between those points. This is a common feature across the audi key shell 80-100-200-RS2 model, ranging from the 1985 MC up to the 1997 UrS AN and the 1995 RS2 Du You may also find good ones in wrecking yards.