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How to Replace an Audi G28 Engine Speed Sensor

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

1. Engine Speed Sensor

Located on the edge of the transmission above the flywheel ring gear, the G28 Engine Speed Sensor sends signals to ECU pin T55/49 using the grey wire. The ECU then uses this information to control fuel, timig and boost. It also sends a signal to the G5 Tachometer located in the instrument cluster.

lost audi key serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu has to be aware of when the crankshaft has reached TDC, and the position of the camshaft, so that it can activate the spark and injectors.





If this sensor fails the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of 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 since there are different pins on the connector 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 functional, it should read about 1000 ohms. If you're having issues with this component, look for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, while accelerating from the highway paytoll at a high speed I noticed a massive drop in power. It was as if the engine was running out of gas. Or, my injectors weren't firing. This morning i pull out the spark plugs, 3 were drenched with gazoline the 4th one was dry. When I start the engine, there are no sparks, i place a tissue on the top of each of the injector holes and the 3 drenched with gazoline jump out but the 4th stays closed. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 I get zero ohm. Therefore, i think the issue is somewhere else.

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

I'm not sure what to do, but i feel i have pretty much ruled out everything else. However, i'm afraid that I might have missed something. Let me know If you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 receives a signal from 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. It is easy to find the spare in a salvage shop or parts store. It is simple to test them - just put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that must be aware of the speed and position of the crankshaft in order to make decisions about timing of the fuel injectors, etc. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go badly, you will see codes on the diagnostic scanner that can lead to engine shutdown.

A damaged G28 sensor can cause an inaccurate gearbox speed counter and a gearbox which shifts faster than normal, and/or a misfire while in the gear. If you experience any of these problems, it is most likely that your sensor is failing and should be replaced. The good news is that they are very cheap and easy to find, especially in the case of a Bosch sensor, which is what ours are. If you prefer, GM's version of this part would be a good option.

5. Tachometer

A malfunctioning engine speed sensor could be a cause for many issues in your vehicle. It's a vital component of your Audi's transmission, because it communicates to the ECU about how the car'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 outside of the transmission just above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 through an uncolored wire. The ECU uses this signal to control fuel and boost, and also to timigrate. It also relays 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 [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see approximately 1000 ohms resistance between those two pins. This part is common across the Audi 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS AN and the 1995 RS2 DU So, you may find them in wrecking yards.