How to Replace an Audi G28 Engine Speed Sensor

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

1. Engine Speed Sensor

The grey wire is located on the edge of transmission, just above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU uses this information to control boost and fuel. It also sends signals to the G5 Tachometer located in the instrument cluster.

The sensor is used to correlate the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can activate spark and injectors in the right way.

If this sensor fails when it fails, the ECU will display a P00160 error message. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also indicate a chain stretch or a jumped chain link in the upper chain. 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 most effective method of testing it is by measuring resistance between the sensor Key For Audi and the ECU. When the sensor is functional, it should read about 1000 ohms. If you're experiencing issues with this part, check for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, when i was accelerating to the fullest speed from highway paytoll, i experienced a big cut in power like the engine is out of gas or the injectors aren't firing anymore. I pulled out the spark plugs this morning, 3 were soaked with gasoline and the fourth was dry. When I start the engine, there are no 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 shut. I tested the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got zero Ohm. So i assume the problem is somewhere else.

I also tried to reset PID without success. The car can start when the G28 is not plugged in and it runs perfectly when it is connected, but still has intermittent misfire issues at higher RPM. The temperature sensor for the 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 bar when the actual pressure is 0.

I'm not sure what to do, i think i've pretty much ruled out everything else. I'm afraid i may have missed something. If anyone has suggestions, please share them! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter functions similarly to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily locate the spare in a salvage shop or a parts store. Testing them is easy - put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's side). They should be infinite ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that needs to know the speed and position of the crankshaft to make decisions regarding fuel injector timing etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these go bad you will get codes on the diagnostic scanner which could cause engine shut down.

Some of the symptoms of a failed G28 sensor include an inaccurate rev counter key for audi the gearbox and gears that shift faster than normal and/or misfiring when you are in gear. If you have any of these issues it is most likely that your sensor is deteriorating and requires replacement. The good news is that they are quite affordable and easy to find, especially if you're looking at an Bosch unit like ours. Alternatively, the GM version of this unit is also a great option.

5. Tachometer

A faulty engine speed sensor could be a cause for many issues with your car. It is an important part of the transmission of your Audi, as it transmits information to the ECU on how fast or slowly the engine of the car is turning. When this sensor fails, it can affect the performance of the transmission, as well as the rest of the car's components.

The G5 engine speed sensor is located at the outside of the transmission, above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU then processes the signal to control fuel, timig and boost and then transmitting it to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by checking 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 [79trace [79]), and between pin T6a/1 and pin T26a/12. There should be the resistance to be around 1000 ohms between these two points. This part is common across the audi a3 replacement key 80-100-200-RS2 range, from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 DU You may also find some good ones in wrecking yards.