How to Replace an audi tt key G28 Engine Speed Sensor

Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is situated on the edge 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

The grey wire is located on the outside of the transmission, directly above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU uses this information to regulate the amount of fuel and boost. It also sends an indicator to the G5 Tachometer within the instrument cluster.

The sensor is used to correlate the G40 Camshaft position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can start spark and injectors according to the situation.

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

It's a bit tricky to test since there are several connector pins, and each has its own functions. The best method for doing this is to measure the resistance between the ECU and the sensor. It should read approximately 1000 ohms when the sensor is in full operation. Look for evidence of coolant or oil in the connector bay if there are issues with this part.

2. Injectors

Yesterday accelerating full speed from highway paytoll i had a big cut in power like the engine is running out of gas or the injectors aren't firing anymore. I took out the spark plugs this morning, three were soaked in gasoline, and the fourth was unclean. When I start the engine with no sparks i put tissue on top of each injector hole and the 3 that were drenched in gazoline pop out, but the 4th stays shut. I tested the ground connection of ECU pins 14,30 and 48/55. I found zero ohm. I think the issue is elsewhere.

I also tried to reset the PID without success. The car will start when the G28 is disconnected, but it works fine when the G28 connected. However, the intermittent misfire problem still occurs at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is 0.

I'm not sure what to do, but i think i've pretty much ruled out everything else. I'm afraid i may have missed something. Let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal by the RPM sensor. The GM-style sensor is the same as the G4 and both function in the 80 100 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or at a parts store. Testing them is easy - put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black connector's side). They should be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY) engines needs to know both the position and speed the crankshaft to make decisions regarding timing of the fuel injector, etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go wrong, you will receive codes on the diagnostic scanner that can cause the engine to shut down.

Some of the signs of a failing G28 sensor are an inaccurate rev counter in the gearbox, gears shifting quicker than normal and/or misfiring when you are in gear. If you have any of these issues, it is likely your sensor is going bad and should be replaced. The good news is they are very cheap and easily accessible particularly if you're looking at the Bosch model, which is what ours are. If you prefer, GM's version of this part would be a good option.

5. Tachometer

A malfunctioning engine speed sensor could be the cause of numerous problems in your vehicle. It's an essential component of the transmission of your audi q7 replacement key, as it transmits information to the ECU about how fast or slowly the engine of the car is spinning. This sensor can cause the transmission to fail and other components of the car to be affected.

The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It sends an electrical signal through gray wire to ECU pin T55/49. The ECU then processes this signal to regulate fuel, timig, and boost, and also sends it on to the G5 Tachometer located in the instrument cluster. You can check the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see around 1000 ohms of resistance between those two pins. This is a typical part that is found across the audi a3 key 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.