How to Replace an audi key fob replacement G28 Engine Speed Sensor

Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. This sensor is located on the outside of the transmission just above the flywheel gear. It transmits a signal to the ECU via a grey wire T55/49, then to the tachometer located on the instrument cluster.

1. Engine Speed Sensor

The sensor is located at the edge of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends signals to ECU pin T55/49 through a grey wire. The ECU utilizes this information to control fuel and boost. It also sends an indicator to the G5 Tachometer in instrument cluster.

The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is located so that it can activate spark and injectors according to the situation.

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

It can be a bit difficult to test because there are various connector pins, and each one has different functions. The best method for doing this is to measure the resistance between the ECU and the sensor. If the sensor audikey is operational, it should be reading about 1000 ohms. Examine for signs of coolant or oil in the connector bay if there are problems with this part.

2. Injectors

Yesterday, while accelerating from the highway paytoll at full speed, i noticed a huge reduction in power. It was as if the engine was running out of gas. Or, my injectors were not firing. I took out the spark plugs this morning and found that 3 were soaked in gasoline, and the 4th was dry. When I crank the engine, there are no sparks, I put a piece of tissue on the top of each of the injector holes and the 3 drenched with gazoline jump out but the 4th stays shut. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 i get zero Ohm. I'm assuming the issue is in another place.

I also tried to reset the PID without success. The car will start if the G28 is not plugged in and it runs perfectly when it is plugged in but it still has intermittent misfire issues at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value -49c, audikey even if I unplug it. Also, i noticed that the gauge for oil pressure in the cockpit shows 2 bar when the actual pressure is 0.0 when i rev the engine.

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

3. Fuel Pump

The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or parts store. Testing them is easy to do - just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's end). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY ADU) engines must know both the speed and position of the crankshaft to make decisions regarding timing of the fuel injector, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you are experiencing issues with either of these, the diagnostic scanner will show codes that could cause an engine shut down.

Some of the symptoms of a failing G28 sensor include an inaccurate rev counter for the gearbox and gears that shift faster than normal and/or a misfire when in gear. It is probable that the sensor is failing and needs to be replaced if you encounter any of these symptoms. The good news is they are very affordable and easy to find particularly in the case of the Bosch model, which is what ours are. Alternately, GM's version this part would be a good option.

5. Tachometer

A damaged engine sensor could cause a number of problems in your car. It's an essential component of the transmission in your Audi since it sends information to the ECU about how fast or slowly the car's engine is turning. This sensor could cause the transmission to fail and other car components to be affected.

The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It transmits a signal via an uncolored wire to the ECU pin T55/49. The ECU then processes this signal to regulate fuel, timig, and boost as well as transmitting it to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. You can also 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. It should show around 1000 ohms of resistance between these two points. This is the same across the Audi 80-100-200-RS2 range, from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 DU You may also find some good ones in wrecking yards.