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How to Replace an audi a3 key fob G28 Engine Speed Sensor

Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located at the edge of transmission over the flywheel gear. It sends a signal to the ECU via an uncolored wire (T55/49) which is then sent to the tachometer located 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 an uncolored wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends an indication to the G5 Tachometer in instrument cluster.

The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can trigger spark and injectors in the right way.

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

Testing is a bit challenging because there are two connector pins, and they perform different functions but the most effective method to test it is to measure resistance between the sensor and the ECU. It should read approximately 1000 ohms when the sensor is operating at its maximum. If you're having issues with this component, look for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday accelerating full speed from highway paytoll, I experienced a big cut in power like the engine is out of gas or injectors are not firing anymore. In the morning, i removed the spark plugs, 3 were drenched in gazoline, the 4th one was dry. When i crank the engine without sparks, i place a tissue on the top of each hole in the injector and the 3 drenched with gazoline jump out but the 4th stay shut. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. I get 0ohm. I'm assuming that the issue is in another location.

I also tried to reset PID without success. The car will start when the G28 is unplugged, and it runs fine with the G28 connected. However, the intermittent misfire problem persists at higher RPM. The coolant sensor (G62) even when unplugged, still shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is zero.

I'm not sure what to do, as i feel i have pretty much ruled out everything else. But i'm worried that I might have missed something. Let me know If you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style sender is identical to 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 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's end facing upwards). They should be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY ADU) engines requires to know the speed and position of the crankshaft to make decisions regarding fuel injector timing, etc. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes badly, you will see codes on the diagnostic scanner which can lead to engine shutdown.

The signs of a failed G28 sensor are an inaccurate rev counter for the gearbox and gears that shift faster than normal and/or a misfire when you are in gear. It is likely that the sensor is failing and needs to be replaced if you notice any of these symptoms. They're inexpensive and easy to locate particularly if they're a Bosch unit like ours. Alternatively, the GM version of this part is also a great option.

5. Tachometer

A faulty engine speed sensor could be a cause for numerous problems in your vehicle. It is a crucial part of the audi tt key fob's transmission since it relays information to the ECU about how fast or slow the car's crankshaft is spinning. This sensor could cause the transmission to malfunction and other components of the car to be affected.

The G5 engine sensor is located at the outskirts of the transmission, over the flywheel ring. It transmits an electrical signal through gray wire to ECU pin T55/49. The ECU utilizes this signal to control the flow of fuel and boost and also to timigrate. 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, between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see approximately 1000 ohms resistance between those two pins. This is a common part that is found across the audi key fob 80 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.