How to Replace an audi tt key G28 Engine Speed Sensor

Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. The sensor is located at the top of the transmission above the flywheel ring gear. It transmits a signal to the ECU through a grey wire T55/49, then to the tachometer located on the instrument cluster.

1. Engine Speed Sensor

It is located on the outside of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends signals to ECU pin T55/49 via an uncolored wire. The ECU uses this information to regulate boost and fuel. It also sends an indication to the G5 tachometer inside the instrument cluster.

The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft has reached TDC, and the location of the camshaft to trigger the spark and injectors.

If this sensor fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of an issue with the chain or a jumpy chain link in the upper chain. The code won't appear without the additional information provided by other sensors (G4 or G40).

Testing can be a bit difficult since there are two connector pins, and they serve different purposes however the best way to test it is by measuring resistance between the sensor and the ECU. When the sensor is fully operational, it should be reading about 1000 ohms. Look for signs of coolant or oil in the connector bay if you are experiencing problems with this part.

2. Injectors

Yesterday, while accelerating from the highway paytoll at a high speed I noticed a massive drop in power. It was as if the engine had run out of gas. Or, my injectors were not firing. Today, i pulled out the spark plugs, three were drenched in gazoline, the fourth one was dry. When i crank the engine, there are no sparks i put tissue on top of each injector hole and the 3 drenched with gazoline pop out, but the 4th one stays shut. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. i get 0ohm. So i assume the problem is in another place.

I also tried to reset the PID with no success. The car can start when the G28 is unplugged and runs fine when it is connected, but still has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even when it is unplugged, shows a temperature of -49c. Also i noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when i rev the engine.

I'm not certain what to do, as i think i've pretty much 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 of 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 from a parts store. It is simple to test them by putting your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector end up) and 2 (2nd from the left on the black end of the connector). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that must be aware of the speed and position of the crankshaft to make a decision about timing of the fuel injectors, etc. To accomplish this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go badly, you will see codes on the diagnostic scanner that can lead to engine shutdown.

A failing G28 sensor could result in an inaccurate gearbox speed counter and a gearbox which shifts more quickly than normal, and/or a misfire while in gear. If you are experiencing any of these issues, it is likely your sensor is failing and replacement audi a3 key should be replaced. The good thing is that they are quite affordable and readily available, replacement Audi A3 Key especially if you're looking at a Bosch model, which is what we have. Alternatively, the GM version of this part is also a good choice.

5. Tachometer

A failing engine sensor could cause a number of problems in your vehicle. It's a crucial component of the transmission in your replacement audi A3 key because it relays information to the ECU about how fast or slowly the engine of the car 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 outskirts of transmission, above the flywheel ring. It sends an electrical signal through a gray wire to the ECU pin T55/49. The ECU uses this signal to regulate the flow of fuel and boost and also to timigrate. It also relays it to the G5 Tachometer in instrument cluster. You can check 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 [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see approximately 1000 ohms of resistance between those two pins. This is a typical component across the Audi 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.