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 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 on the instrument cluster.

1. Engine Speed Sensor

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

The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft has reached TDC and also where the camshaft lies in order to activate the spark and injectors.

If this sensor fails, the ECU will show a P00160 code which means the Crank Shaft and Intake Camshaft are not in sync, possibly indicating the chain stretching or a jump link on the upper timing chain. The code won't show without the additional information provided by other sensors (G4 or G40).

Testing can be a bit difficult as there are two different pins for the connector and they serve different purposes but the best method of testing it is to measure the resistance between the sensor and the ECU. It should read around 1000 ohms when it is operating at its maximum. Look for evidence of coolant or oil in the connector bay if you are experiencing problems with this part.

2. Injectors

Yesterday accelerating full speed from highway paytoll, I experienced an abrupt drop in power like the engine is running out of gas or injectors are not firing at all. I pulled out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was unclean. I put tissue over each injector hole and when i start the engine with no sparks, the ones with gazoline jump right out. The fourth one remains shut. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. I got 0ohm. I think the issue is in another location.

I also tried to reset the PID but without success. The car can start if the G28 is not plugged in and runs fine when it is plugged in, but still is experiencing intermittent misfires at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is zero.

I'm not sure what to do. I feel like i've pretty much all other possibilities out. However, i'm afraid that i might have missed something. If anyone has any ideas please let me know! TIA!

3. Fuel Pump

The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style transmitter is similar to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily locate an extra in a wrecking shop or parts store. It is simple to test them: simply switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that must know the position and speed of the crankshaft in order to make decisions regarding timing of the fuel injectors, etc. To accomplish this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either one of these, the diagnostic scanner will show codes that could cause an engine shut down.

A malfunctioning G28 sensor can cause an inaccurate gearbox speed counter or a gearbox that shifts more quickly than normal, and/or a misfire in the gear. If you experience any of these issues, it is most likely that your sensor is deteriorating and requires replacement. They are cheap and easy-to-find especially in the case of an Bosch sensor like ours. Alternately, the GM version of this part is also a great option.

5. Tachometer

A malfunctioning engine sensor can cause a number of problems within your vehicle. It's a crucial component of the transmission in your audi car keys, as it transmits information to the ECU regarding how fast or slowly the engine of the car is turning. When this sensor fails, it can disrupt the performance of the transmission as well as the other car's components.

The G5 engine sensor is located at the edge of the transmission, over the flywheel ring. It sends signals via an uncolored wire to the ECU pin T55/49. The ECU then processes this signal to control fuel, timig, and boost and then transmitting it to the G5 tachometer in the instrument cluster. You can test for sensor failure by examining the 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 [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 car key holder 80 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best ones could be available in wrecking yards.