How to Replace an Audi G28 Engine Speed Sensor

In this video, Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is situated near the edges of the transmission above the flywheel ring gear. It sends a message to the ECU through a grey wire T55/49, then to the tachometer in the instrument cluster.

1. Engine Speed Sensor

The grey wire is located on the edge of transmission, directly above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU utilizes this information to regulate the amount of fuel and boost. It also sends an indication to the G5 Tachometer located in 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 has reached TDC and also the position of the camshaft, to trigger the spark and injectors.

If this sensor fails the ECU will throw the P00160 error, 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. However the code will not be displayed on its own without additional information from other sensors (G4 and G40).

It is a little tricky to test since there are different connector pins, and they all have different functions. The best method for doing this 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 having 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 massive drop in power. It was like the engine was running out of gas. Or, my injectors weren't firing. This morning i pull out the spark plugs. Three were drenched with gazoline the fourth one was dry. When I start the engine, there are no sparks, I put a piece of tissue on the top of each hole in the injector and the 3 drenched with gazoline pop out, but the 4th one stays shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I got 0ohm. I'm assuming the issue is elsewhere.

I also tried to reset the PID but without success. The car is able to start if the G28 is disconnected and it runs perfectly when it is plugged in, but still is experiencing intermittent misfires at higher RPM. The coolant sensor (G62), even when it is unplugged, shows an ice temperature of -49c. I also noticed website that the oil pressure gauge in the cockpit is showing 2 bar when the actual pressure is 0.0 when i rev the engine.

I don't know what to do. I feel like i've pretty much all audi a1 keys other possibilities out. However, i'm afraid that i might have missed something. If anyone has suggestions, please share them! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal from the website RPM sensor. The GM-style transmitter functions similarly 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. It website is easy to test them: simply put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They must be infinite ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY, and ADU) engines are equipped with an ECU that must know the speed and position of the crankshaft in order to make a decision about fuel injector timing etc. To do this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes bad you will get codes on the diagnostic scanner that could cause engine shut down.

Some of the symptoms of a failing G28 sensor are an inaccurate rev counter for the gearbox and gears that shift faster than normal and/or misfiring when you're in gear. If you are experiencing any of these issues, it is most likely that your sensor is deteriorating and should be replaced. They're cheap and easy to find especially in the case of an Bosch sensor like ours. Alternately, the GM version of this component is also a good choice.

5. Tachometer

A failing engine sensor could cause a number of problems in your car. It is an important part of the transmission of your Audi since it sends information to the ECU about how fast or slowly the car's engine is turning. If the sensor fails, it could affect the performance of the transmission and the other car's get more info 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 is then able to process this signal to control fuel, timig, and boost and then sends it on to the G5 tachometer inside the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. It should show approximately 1000 ohms resistance between those points. This is a typical component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.