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

Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. The sensor is situated at the top of the transmission just above the flywheel ring gear. It sends a message 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 just above the flywheel ring gear G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using an uncolored wire. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends signals to the G5 tachometer inside the instrument cluster.

The sensor is used to correlate the G40 Camshaft position Sensor. The ecu must know when the crankshaft reached TDC, and the location of the camshaft so that it can activate the spark and injectors.

If this sensor fails when it 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 timing chain. The code won't appear without the additional information provided by other sensors (G4 or G40).

It is a little tricky to test because there are several pins on the connector and each has its own functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. When the sensor is fully operational, it should be reading around 1000 ohms. Check for evidence of coolant or oil in the connector bay if you are experiencing issues with this part.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll, i experienced an abrupt drop in power as if the engine was running out of gas or injectors aren't firing anymore. This morning i pull out the spark plugs. Three were drenched with gazoline the fourth was dry. I placed a tissue over each injector hole and when I turn the engine on without sparks, the three with gazoline jump out. The 4th one stays closed. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. I got zero Ohm. I'm assuming that the issue is elsewhere.

I also tried to reset the 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 temperature sensor (G62) shows the wrong temperature of -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is zero.

I'm not sure what to do, as i think i've pretty much ruled out everything else. 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 is activated by a signal by the RPM sensor. The GM-style sensor is identical to the G4 and both are used in the 80 100 200, UrS and RS2 cars so you can easily find one at a wrecking yard or Audi advance Key from a parts store. Testing them is easy - 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 the left on the black end of the connector). They should be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that needs to know 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 you encounter a problem with either of these sensors, the diagnostic scanner will show codes that could lead to an engine shutdown.

A failing G28 sensor can cause an inaccurate gearbox speed counter or a gearbox that shifts faster than normal, and/or a misfire in gear. It is probable that your sensor is failing and needs to be replaced if you encounter any of these signs. They're cheap and easy to find particularly when they're an Bosch unit like ours. Alternatively, the GM version of this component is also a good option.

5. Tachometer

A damaged engine sensor could cause a number of problems in your vehicle. It's a vital component of the Audi Key Shell's transmission because it communicates to the ECU about how fast or slow the car's crankshaft is rotating. This sensor can cause the transmission to fail and other components of the car to be affected.

The G5 engine speed sensor is located at the outside of the transmission just above the flywheel ring gear and sends a signal to the ECU at pin T55/49, new Audi keys via a grey wire. The ECU then processes this signal to regulate fuel, timig, and boost and then sends it on to the G5 tachometer in the instrument cluster. You can determine if the sensor is in 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. You should observe around 1000 ohms of resistance between these two points. This is the same across the audi replacement key service near me 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS An and 1995 RS2 DU You may also find some good ones in wrecking yards.