How to Replace an audi Car key Case G28 Engine Speed Sensor

In this video Charles the Humble Mechanic shows how to replace audi key fob the G28 engine speed sensor. This sensor is located on the outside of the transmission, above the flywheel gear. It transmits a signal to the ECU via a grey wire (T55/49) and then to the tachometer in the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated at the edges of the transmission, directly above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends signals to the G5 tachometer in the instrument cluster.

The sensor is used to link with the G40 Camshaft position Sensor. The ecu must know when the crankshaft has reached TDC and also where the camshaft lies so that it can activate the spark and injectors.

If this sensor fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jump in the chain link of the upper chain of timing. However, the code won't appear on its own, without additional information from other sensors (G4 and G40).

Testing is a bit challenging since there are two connector pins and they perform different functions but the best way to test it is to measure the resistance between the sensor and the ECU. It should read about 1000 ohms when it is in full operation. If you're experiencing issues with this sensor, look for signs of oil or coolant in the connector bay.

2. Injectors

Yesterday, while accelerating from the highway paytoll at full speed, i noticed a huge decrease in power. It was as if the engine had run out of gas. Or my injectors weren't firing. I pulled out the spark plugs this morning, three were soaked in gasoline, and the fourth was dry. I put a piece of tissue over each hole in the injector and when i start the engine without sparks, the three that have gazoline pop right out. The 4th one remains shut. I checked 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 with no success. The car is able to start if the G28 is not plugged in and runs fine when it is plugged in however it is experiencing intermittent misfires at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of -49c even when i unplug it. Also i noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.

I don't know what to do. I think I've all other possibilities out. I'm concerned that i may have missed something. If anyone has any suggestions, please chime in! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal sent 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 salvage yard or at a parts store. It is easy to test them: simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They must be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY) engines must know the speed and position of the crankshaft to determine timing of the fuel injector, etc. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either of these, the diagnostic scanner will display codes that could lead to an engine shut down.

The signs of a malfunctioning G28 sensor are an inaccurate gearbox rev counter and gears that shift faster than normal and/or misfiring when you are in gear. It is probable that your sensor is failing and needs to be replaced if you encounter any of these signs. They are cheap and easy-to-find particularly when they're an Bosch unit like ours. If you prefer, GM's version of this component is an option.

5. Tachometer

A damaged engine sensor could cause a myriad of issues in your car. It's an essential component of your Audi's transmission, because it communicates to the ECU about how fast or slow the vehicle's crankshaft is rotating. This sensor could cause the transmission to malfunction and other components in the car to be affected.

The G5 engine speed sensor is located on the edge of the transmission, above the flywheel ring gear and sends a signal to the ECU at pin T55/49, via an uncolored wire. The ECU then processes this signal to control fuel, timig and boost as well as transmitting it to the G5 tachometer inside the instrument cluster. You can check for sensor failure by examining the continuity of the sensor to the tachometer. Additionally, you can check continuity between pin T55/49 of the ECU and Audi car key case 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 those points. This is the same across the Audi 80-100-200-RS2 range, from the 1985 MC all the way up to the 1997 UrS An and 1995 RS2 DU So, you may find good ones in wrecking yards.