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

Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. This sensor is located near the edges of the transmission above the flywheel ring gear. It transmits a signal to 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 a signal to ECU pin T55/49 using a grey wire. The ECU utilizes this information to control the amount of fuel and boost. It also sends signals 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 has to be aware of when the crankshaft has reached TDC, and the position of the camshaft, to trigger the spark and injectors.

If this sensor fails when it fails, the ECU will display a P00160 error code. This indicates that the Crank Shaft is out of sync with the Intake Camshaft. It could also indicate an issue with the chain or Audi new key a jump in the chain link of the upper timing chain. However the code will not be displayed on its own without additional information from other sensors (G4 and G40).

It is a little tricky to test because there are various connector pins, and each one has different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. When the sensor is fully operational, 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, while accelerating from the highway paytoll at maximum speed I noticed a massive drop in power. It was like the engine had run out of gas. Or, my injectors weren't firing. I pulled out the spark plugs this morning, three were soaked with gasoline and the fourth was unclean. I put tissue over each injector hole and when I turn the engine on without sparks, the three that have gazoline pop right out. The 4th one stays shut. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 I get 0ohm. I'm assuming the issue is elsewhere.

I also tried to reset PID but without success. The car will start when the G28 is disconnected and it runs perfectly when it is connected however it has intermittent misfire issues at higher RPM. The coolant sensor (G62) even when it is unplugged, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is zero.

I don't know what to do. I believe that I've eliminated everything else. I'm concerned that i may have missed something. If anyone has any ideas please let me know! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal sent from the RPM sensor. The GM-style sender is identical to the G4 and they both work in the 80, 100 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or in a local parts store. It is easy to test them: simply put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They should be infinite ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that has to know the speed and position of the crankshaft in order to make decisions regarding timing of the fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either of these sensors, the diagnostic scanner will display the codes that could trigger the engine shutting down.

A failing G28 sensor could cause an inaccurate speed counter for the gearbox and a gearbox which shifts faster than normal, or a misfire while in gear. If you experience any of these issues, it is most likely that your sensor is deteriorating and should be replaced. The good news is that they are very cheap and easy to find, especially in the case of an Bosch unit which is what we have. If you prefer, GM's version of this component is an excellent choice.

5. Tachometer

A failing engine speed sensor could be the cause of numerous issues with your vehicle. It is a crucial part of your Audi new Key's transmission, since it relays information to the ECU about how fast or slow the vehicle's crankshaft is turning. This sensor can cause the transmission to malfunction and other components in the car to be affected.

The G5 engine sensor is located at the edge of the transmission, over the flywheel ring. It sends an electrical signal through gray wire to ECU pin T55/49. The ECU then processes this signal to control fuel, timig, and boost, and also sends it on to the G5 Tachometer located in the instrument cluster. You can test for sensor failure by examining the continuity from the sensor to the tachometer. You can also examine the continuity between pins 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 approximately 1000 ohms resistance between these two points. This is a typical component across the audi new key 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.