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Why No One Cares About Audi G28
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. This sensor is situated at the edge of transmission just above the flywheel gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer in 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 transmits a signal via the grey wire to pin T55/49. The ECU utilizes this information to control the amount of fuel and boost. It also sends an indication to the G5 tachometer in the instrument cluster.

The sensor is used to link with the G40 Camshaft position Sensor. The ecu must be aware when the crankshaft is TDC and the location of the camshaft so it can activate spark and injectors accordingly.

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 the chain is stretched or a jump link on the upper chain of timing. The code won't appear without the additional information provided by other sensors (G4 or G40).

It can be a bit difficult to test as there are different pins on the connector, and each has its own functions. The best way to do it is to measure the resistance between the ECU and the sensor. It should read about 1000 ohms if the sensor is in full operation. Check for signs of coolant or oil in the connector bay if you have problems with this part.

2. Injectors

Yesterday accelerating full speed from highway paytoll, I experienced massive power loss like the engine is out of gas or injectors are not firing any more. In the morning, i removed the spark plugs, 3 were drenched in gazoline, the 4th one was dry. I put tissue over each injector hole, and when I start the engine with no sparks, the three with gazoline jump right out. The 4th one stays closed. I checked the ground connection of ECU pins 14,30 and 48/55. I found zero ohm. I'm assuming the issue is somewhere else.

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 connected. However, the intermittent misfire problem still occurs at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature value of -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0.

I'm not sure what to do, as i feel i have pretty much ruled out everything else. However, i'm afraid that I may have missed something. Please let me know should you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal sent from the RPM sensor. The GM-style sender is identical to 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. It is easy to test them - just put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). new audi key must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines needs to know both the position and speed of the crankshaft to determine timing of fuel injectors, etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these sensors, the diagnostic scanner will display the codes that could trigger an engine shut down.

A failing G28 sensor could cause an inaccurate gearbox speed counter or a gearbox that shifts faster than normal, or a misfire while in gear. It is possible that the sensor is failing and requires to be replaced if you encounter any of these symptoms. The good news is they are very cheap and readily available, especially if you're looking at a Bosch sensor, which is what we have. If you prefer, GM's version of this part would be an excellent choice.

5. Tachometer

A damaged engine sensor could cause a myriad of issues in your car. It is a crucial part of your Audi's transmission, as it sends information to the ECU about how the car's crankshaft is rotating. When this sensor fails, it will affect the performance of the transmission and the rest of the car's components.

The G5 engine speed sensor is located on the edge of the transmission above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU utilizes this signal to control the amount of fuel and boost, and also timig. It also transmits it 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. You should see a resistance of approximately 1000 ohms between these two points. This is a common part across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU, so the best ones might be availble in wrecking yards.

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