How to Replace an Replacement Audi Key fob G28 Engine Speed Sensor

Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. The sensor is located on the edge of the transmission above the flywheel ring gear. It transmits a signal the ECU via the grey wire (T55/49) and then to the tachometer within the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated at the edges of the transmission, just above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an alert to the G5 Tachometer located in the instrument cluster.

The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft reached TDC and also the location of the camshaft so that it can activate the spark and injectors.

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

Testing is a bit tricky as there are two different connector pins and they serve different purposes but the best method to test it is to measure the resistance between the sensor and the ECU. When the sensor is operational, it should read about 1000 ohms. If you're experiencing issues with this part, check for evidence of oil or coolant in the connector bay.

2. Injectors

Yesterday, while accelerating from the highway paytoll at a high speed I noticed a significant drop in power. It was as if the engine had run out of gas. Or my injectors were not firing. I took out the spark plugs this morning, 3 were soaked in gasoline, and the 4th 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 that were drenched in gazoline leap out, however the 4th stays closed. I tried to test the ground connections of ECU pins 14,30, and 48/55. I found zero ohm. I'm assuming the issue is elsewhere.

I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it is running fine with the G28 plugged in. However the intermittent misfire issue persists at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is zero.

I'm not sure what to do. I think I've all other possibilities out. I'm concerned that i may have missed something. Let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter is identical to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily locate the spare in a salvage shop or parts store. Test them out by putting your DMM in resistance mode and take measurements 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 should be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY) engines needs to know both the speed and position of the crankshaft in order to make a decision about timing of fuel injectors, 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 that could cause engine shut down.

Some of the symptoms of a failed G28 sensor include an inaccurate gearbox rev counter and gears that shift faster than normal, and/or a misfire when you're in gear. If you have any of these issues it is most likely that your sensor is failing and Audi A3 Spare Key should be replaced. The good thing is that they are very affordable and easy to find, especially if you're looking at a Bosch model, like ours. Alternately, GM's version this part would be an option.

5. Tachometer

A failing engine sensor could cause a myriad of issues in your car. It is an important part of the transmission in your audi car key since it sends information to the ECU on how fast or slowly the engine of the car is spinning. This sensor can cause the transmission to fail and other components in the car to be affected.

The G5 engine speed sensor is situated on the edge of the transmission above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 via a grey wire. The ECU then uses and processes this signal to control fuel, timig, and boost and then transmitting it to the G5 tachometer in the instrument cluster. You can check for sensor failure by examining the continuity from the sensor to the tachometer. Additionally, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 as well as pin T26a/12. You should observe approximately 1000 ohms of resistance between those two pins. This is a common feature across the audi tt replacement key 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS AN and the 1995 RS2 DU You may also find some good ones in wrecking yards.