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

Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. The sensor is located on the edge of the transmission just above the flywheel ring gear. It transmits a signal to the ECU via the grey wire T55/49 and then to the tachometer located 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 through an uncolored wire. The ECU utilizes this information to regulate the amount of fuel and boost. It also sends an alert to the G5 Tachometer within the instrument cluster.

The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and the location of the camshaft so it can trigger spark and injectors in the right way.

If this sensor fails when it fails, the ECU will display an error code P00160. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also indicate an issue with the chain or a jump in the chain link of the upper timing chain. The code will not appear without the additional information provided by other sensors (G4 or G40).

Testing is a bit tricky since there are two connector pins and they perform different functions but the most effective method to test it is to measure the resistance between the sensor and the ECU. It should read about 1000 ohms if the sensor is at full operation. If you're having issues with this part, check for signs of oil or coolant in the connector bay.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll, i experienced a big cut in power as if the engine was running out of gas or injectors are not firing anymore. Today, i pulled out the spark plugs, 3 were drenched with gazoline the 4th one was dry. When I start the engine with no sparks, i place a tissue on top of each injector hole and the 3 drenched with gazoline leap out, however the 4th one stays shut. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I get 0ohm. I think the issue is in another location.

I also tried to reset the PID without success. The car can start when the G28 is unplugged and runs fine when it is connected but it still has intermittent misfire issues at higher RPM. The coolant temperature sensor (G62) shows the wrong temp value -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0.

I don't know what to do. I feel like i've pretty much ruled everything else out. I'm worried that i might have missed something. Let me know should you have any suggestions! TIA!

3. Fuel Pump

The fuel pump on the g28 is activated by a signal from the RPM sensor. The GM-style sensor is the same as the G4 and they both work in the 80, 100, 200, UrS and RS2 cars so you can easily find one at a junkyard or in a local parts store. It is simple to test them by putting your DMM in resistance mode and measure between pins 1 (with the bump on the connector end up) and 2 (2nd from 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 has to know the position and speed of the crankshaft in order to make decisions regarding timing of the fuel injectors, etc. It uses 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 show codes that could lead to an engine shut down.

The signs of a failed G28 sensor include an inaccurate gearbox rev counter the gears are shifting faster than normal and/or misfiring when you're in gear. It is probable that the sensor is failing and requires to be replaced if you experience any of these symptoms. They're cheap and easy to find particularly if they're an Bosch unit like ours. Alternately, GM's version this part would be a good option.

5. Tachometer

A failing engine speed sensor could be the cause of numerous problems in your vehicle. It is an important part of the transmission in your audi remote key since it sends information to the ECU about how fast or slowly the car's engine is spinning. If the sensor fails, it can affect the performance of the transmission and the other audi car keys's components.

The G5 engine sensor is located at the outskirts of the transmission, over the flywheel ring. It sends signals via a gray wire to the ECU pin T55/49. The ECU then processes the signal to control the flow of fuel, timig and boost, and also sends it on to the G5 tachometer inside the instrument cluster. You can check the sensor key for audi any failure by checking the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. There should be a resistance of approximately 1000 ohms between these two points. This is a standard part that is found across the audi etron key 80 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best ones might be availble in wrecking yards.