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How to Replace an audi car key holder G28 Engine Speed Sensor

In this video, Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is located near the transmission's edge, above the flywheel 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 sensor is located at the edge of the transmission above the flywheel ring gear G28 Engine Speed Sensor sends signals to ECU pin T55/49 through a grey wire. The ECU utilizes this information to control fuel and boost. It also sends an indicator to the G5 Tachometer located in the instrument cluster.

The sensor is used to link the G40 Camshaft position Sensor. The ecu has to know when the crankshaft reached TDC and also the location of the camshaft to trigger the spark and injectors.

If this sensor fails the ECU will throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync and possibly indicating the chain stretching or a jump link on the upper timing chain. The code will not appear without the additional information provided by other sensors (G4 or G40).

It can be a bit difficult to test since there are various pins on the connector and each has its own functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. When the sensor is fully functional, it should read about 1000 ohms. Examine for signs of coolant or oil in the connector bay if there are issues with this part.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll, i experienced an abrupt drop in power like the engine is running out of gas or the injectors aren't firing anymore. I pulled out the spark plugs this morning, three were soaked with gasoline and the 4th was dry. I put a piece of tissue over each injector hole and when I start the engine without sparks, the three with gazoline jump right out. The fourth one remains closed. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I get zero Ohm. I think the issue is in another location.

I also tried to reset PID without success. The car is able to start when the G28 is disconnected and is running fine when it is plugged in however it is experiencing intermittent misfires at higher RPM. The coolant temperature sensor (G62) shows the wrong temp value that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is 0.

I don't know what to do. I feel like i've pretty much all other possibilities out. However, i'm afraid that I may have missed something. Let me know If you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal from the RPM sensor. The GM-style sensor is the same as the G4 and both are used in the 80 100, 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or at a parts store. It is easy to test them - just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector's end facing up). They should be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines needs to be aware of the position and speed 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 achieve this. If either of these goes wrong, you will receive codes on the diagnostic scanner that could cause engine shut down.

A damaged G28 sensor can cause an inaccurate speed counter for the gearbox, a gearbox that shifts faster than normal, or a misfire in gear. If you are experiencing any of these issues, it is likely your sensor is deteriorating and requires replacement. They are 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 a cause for numerous problems in your car. It's an essential component of your audi key fob's transmission, because it communicates to the ECU about how fast or slow the car's crankshaft is turning. If this sensor fails, it will affect the performance of the transmission and the other car's components.

The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It transmits a signal via gray wire to ECU pin T55/49. The ECU then processes the signal to control the flow of fuel, timig and boost as well as sends it on to the G5 tachometer inside the instrument cluster. You can determine if the sensor is in failure by examining the continuity of 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 [79]) and between pin T6a/1 and pin T26a/12. You should see approximately 1000 ohms resistance between those two pins. This is a standard part that is found across the audi car key replacement 80, 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.