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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 near the transmission's edge just above the flywheel gear. It sends a message to the ECU via a grey wire T55/49, then to the tachometer located on the instrument cluster.

1. Engine Speed Sensor

The grey wire is located at the edges of the transmission, above the flywheel ring. This sensor sends signals through the grey wire to pin T55/49. The ECU utilizes this information to control the amount of fuel and boost. It also sends signals to the G5 tachometer inside the instrument cluster.

The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is located so that it can activate spark and injectors accordingly.

If this sensor fails when it fails, the ECU will display a P00160 error code. 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. The code won't appear without the additional information provided by other sensors (G4 or G40).

It's a bit tricky to test because there are several connector pins, and they all have different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. When the sensor is functional, it should read approximately 1000 ohms. Look for signs of coolant, or oil in the connector bay if you have issues with this part.





2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll, I experienced massive power loss as if the engine was running out of gas or the injectors aren't firing anymore. visit my webpage took out the spark plugs this morning, three were soaked in gasoline, and the fourth was dry. I put tissue over each injector hole, and when I start the engine without sparks, the 3 that have gazoline pop right out. The 4th one stays shut. I checked the ground connection of ECU pins 14,30 and 48/55. I got zero ohm. I assume that the problem is in another location.

I also tried to reset the PID without success. The car can start when the G28 is not plugged in and it runs perfectly when it is plugged in, but still has intermittent misfire issues at higher RPM. The coolant sensor (G62), even when it is unplugged, shows a temperature of -49c. Also i noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.

I'm not sure what to do. I think I've all other possibilities out. But i'm worried that I may have missed something. If anyone has any suggestions, please share them! TIA!

3. Fuel Pump

The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style sender is the same as the G4 and both are used in the 80 100, 200, UrS and RS2 cars so you can easily find one at a wrecking yard or in a local 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 at the connector end facing upwards). They should be infinite ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY ADU) engines needs to know both the speed and position of the crankshaft to determine timing of fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish 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 failing G28 sensor are an inaccurate rev counter in the gearbox, gears shifting quicker than normal, and/or a misfire when in gear. It is possible that the sensor is failing and needs to be replaced if you experience any of these symptoms. The good news is they are very cheap and easy to find, especially in the case of a Bosch model, like ours. If you prefer, GM's version of this part would be a good option.

5. Tachometer

A failing engine speed sensor could be the cause of numerous problems in your vehicle. It's an essential component of your Audi's transmission, because it communicates to the ECU about how fast or slow the vehicle's crankshaft is rotating. If the sensor fails, it could disrupt the performance of the transmission, as well as the other car's components.

The G5 engine speed sensor is located at the outside of the transmission just above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 via a grey wire. The ECU is then able to process the signal to control the flow of fuel, timig and boost and then sends it on to the G5 tachometer in the instrument cluster. You can check for sensor failure by checking continuity from the sensor to the tachometer. Also, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]), and between pin T6a/1 as well as pin T26a/12. You should see approximately 1000 ohms resistance between those points. This is a typical part that is found across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.