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How to Replace an audi connect key G28 Engine Speed Sensor

Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located near the transmission's edge, above the flywheel gear. It sends a signal to the ECU via an uncolored wire (T55/49) which is then sent to the tachometer in the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via an uncolored wire. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends an alert to the G5 Tachometer located in the instrument cluster.

The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu has to be aware of when the crankshaft has reached TDC, and where the camshaft lies in order to activate the spark and injectors.

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

It can be a bit difficult to test because there are different connector pins, and they all have different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. If the sensor is operational, it should read about 1000 ohms. If you're experiencing issues with this part, check for signs 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 decrease in power. It was like the engine had run out of gas. Or, my injectors weren't firing. I took out the spark plugs this morning, three were soaked in gasoline, and the fourth was unclean. I put tissue over each hole in the injector and when I start the engine with no sparks, the 3 with gazoline jump right out. The 4th one stays closed. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I get zero Ohm. I'm assuming the issue is somewhere else.

I also tried to reset PID but without success. The car will start when the G28 is disconnected, but it works fine when the G28 plugged in. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62) even when it is unplugged, shows a temperature of -49c. Also, i noticed that the gauge for oil pressure in the cockpit is showing 2 bar when the actual pressure is 0.0 when i rev the engine.

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. If anyone has suggestions, please let me know! 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 operate on the 80,100,200, UrS, and RS2 vehicles. You can easily locate a audi a3 spare key in a wrecking shop or a parts store. It is easy to test them - just put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They should be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to be aware of the position and speed of the crankshaft in order to make a decision about timing of fuel injectors, etc. In order to do this it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go bad you will get codes on the diagnostic scanner that can cause the engine to shut down.

The signs of a malfunctioning G28 sensor include an inaccurate gearbox rev counter and gears that shift faster than normal and/or a misfire when you are in gear. It is likely that the sensor is failing and needs to be replaced if you experience any of these signs. The good thing is that they are very cheap and easy to find particularly when you're looking at an Bosch model, which is what we have. Alternately, the GM version of this part is also a good option.

5. Tachometer

A malfunctioning engine sensor can cause a myriad of issues within your vehicle. It is an important part of the transmission in your audi advanced key because it relays 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 rest of the car's components.

The G5 engine sensor is located at the edge of the transmission, over the flywheel ring. It sends a signal via gray wire to ECU pin T55/49. The ECU then processes the signal to control 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 checking continuity between it and audikey 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. There should be an average resistance of 1000 ohms between these points. This is a common feature across the audi key blade 80-100-200-RS2 model, ranging from the 1985 MC all the way up to the 1997 UrS AN and 1995 RS2 Du You may also find them in wrecking yards.