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 located at the top of the transmission above the flywheel ring gear. It sends a signal to the ECU via an uncolored wire (T55/49), then to the tachometer within 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 sends a signal via the grey wire to pin T55/49. The ECU uses this information to control boost and fuel. It also sends a signal to the G5 Tachometer located in the instrument cluster.

The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft has reached TDC, and where the camshaft lies to trigger the spark and injectors.

If this sensor fails, the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync and could indicate chain stretch or a jumped link on the upper timing chain. However, the error code won't be displayed 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 serve different purposes however the best way to test it is by measuring resistance between the sensor and the ECU. It should read about 1000 ohms when it is operating at its maximum. If you're having issues with this component, look for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll i had massive power loss as if the engine was running out of gas or injectors aren't firing any more. I took out the spark plugs this morning, 3 were soaked with gasoline and the 4th was dry. When I crank the engine with no sparks, i place a tissue on top of each injector hole and the 3 that were drenched in gazoline jump out but the 4th one stays shut. I tried to test the ground connections of ECU pins 14,30, and 48/55. I got zero ohm. So i assume the problem is somewhere else.

I also tried to reset the PID but with no luck. The car is able to start if the G28 is not plugged in and is running fine when it is plugged in, 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. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is 0.

I'm not sure what to do. I feel like i've pretty much ruled everything else out. I'm afraid i may more info have missed something. Please let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style sensor is the same as the G4 and both function in the 80 100 200, UrS and RS2 cars which is why you website can easily locate one at a salvage yard or at a parts store. Test them out by putting your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the check here connector's end up) and 2 (2nd from the left on the black end of the connector). They must be infinite ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that needs to know the position and speed of the crankshaft to make a decision about timing more info of the fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you have a problem with either of these sensors, the diagnostic scanner will display the codes that could trigger an engine shutdown.

A damaged G28 sensor could cause an inaccurate gearbox speed counter and a gearbox which shifts faster than normal, or a misfire in gear. If you are experiencing any of these issues it is most likely that your sensor is going bad and requires replacement. They're inexpensive and easy to locate especially if they're a Bosch sensor like ours. You can also choose the GM version of this part is also a great option.

5. Tachometer

A malfunctioning engine sensor can cause a myriad of issues in your vehicle. It's a vital component of the Audi's transmission since it relays information to the ECU about how fast or slow the vehicle's crankshaft is rotating. This sensor could cause the transmission to fail 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. It sends a signal directly to the ECU at pin T55/49, via an uncolored wire. The ECU click here uses this signal to regulate the flow of fuel and boost and also timig. It also transmits it to the G5 Tachometer inside the instrument cluster. You can test the sensor for failure by checking continuity between it and the tachometer, between the 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 observe around 1000 ohms of resistance between those points. This is the same across the Audi 80-100-200-RS2 series, starting from the 1985 MC up to the 1997 UrS AN and the 1995 RS2 DU So, you may find them in wrecking yards.