How to Replace an Audi G28 Engine Speed Sensor

In this video Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. The sensor is located at the top of the transmission above the flywheel ring 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 on the edge of transmission, directly above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU uses this information to regulate boost and fuel. It also sends signals to the G5 tachometer inside the instrument cluster.

The sensor is used to connect with the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft reached TDC and also the location of the camshaft so that it can activate the spark and injectors.

If this sensor fails to function, the ECU will display a P00160 error message. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also indicate an issue with the chain or a jumped chain link in the upper timing chain. However the code will not appear on its own, without additional information from other sensors (G4 and G40).

It can be a bit difficult to test because there are various pins on the connector, and each one has different functions. The best method for doing this is to measure the resistance between the ECU and the sensor. It should read about 1000 ohms when the sensor is operating at its maximum. Look for evidence of coolant or oil in the connector bay if there are issues with this part.

2. Injectors

Yesterday accelerating full speed from highway paytoll i had massive power loss like the engine is out of gas or the injectors are not firing at all. In the morning, i removed the spark plugs. Three were drenched with gazoline the fourth was dry. I put tissue over each injector hole, and when i start the engine without sparks, the ones with gazoline jump right out. The 4th one remains closed. I tested the ground connection on ECU pins 14/55,30/55 and 48/55 I get zero ohm. I assume that the problem is in another location.

I also tried to reset PID but without success. The car will start when the G28 is unplugged, and it works fine when the G28 plugged in. However the intermittent misfire issue continues to occur at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature cost of audi key replacement -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is zero.

I'm not sure what to do. I think I've ruled everything else out. But i am afraid I might have missed something. If anyone has any suggestions, please let me know! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal from the RPM sensor. The GM-style transmitter is the same as 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 from a parts store. Test them out to do - just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black end of the connector). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to know both the position and speed the crankshaft to make decisions regarding timing of the fuel injector, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you have a problem with either of these, the diagnostic scanner will show codes that could lead to an engine shutdown.

The signs of a malfunctioning G28 sensor are an inaccurate rev counter for the gearbox and gears that shift faster than normal, and/or a misfire when you're in gear. It is likely that the sensor costs is failing and needs to be replaced if you experience any of these signs. The good news is that they are very cheap and easy to find particularly if you're looking at a Bosch model, which is what we have. Alternatively, the GM version of this unit is also a great option.

5. Tachometer

A failing engine speed sensor could be a cause for numerous problems in your vehicle. It is an important part of the transmission of your audi key blade, as it transmits information to the ECU regarding how fast or slow the engine of the car is turning. If the sensor fails, it could disrupt 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 Costs sends a signal directly to the ECU at pin T55/49 via an uncolored wire. The ECU uses this signal to regulate fuel and boost, and also to timigrate. It also relays it to the G5 Tachometer located in the instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. There should be the resistance to be around 1000 ohms between these two points. This is a typical component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.