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How to Replace an audi keys 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 over the flywheel gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer located on the instrument cluster.

1. Engine Speed Sensor

It is located on the outside of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends signals to ECU pin T55/49 through an uncolored wire. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an indication to the G5 Tachometer within the instrument cluster.

The sensor serves 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 so it can trigger spark and injectors according to the situation.

If this sensor fails, the ECU will throw 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 show without the additional information provided by other sensors (G4 or G40).

Testing can be a bit difficult as there are two different pins for the connector and they serve different purposes but the most effective way to test it is to measure resistance between the sensor and the ECU. It should read about 1000 ohms when it is at full operation. Look for evidence of coolant or oil in the connector bay if you have problems with this part.

2. Injectors

Yesterday, when accelerating from highway paytoll at maximum speed I noticed a significant decrease in power. It was like the engine had run out of gas. Or, my injectors weren't firing. I took out the spark plugs this morning, three were drenched in gasoline and the fourth was unclean. When i crank the engine, there are no sparks, i place a tissue on top of each injector hole, the 3 drenched with gazoline leap out, however the 4th stays closed. I tested the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. So i assume the problem is somewhere else.

I also tried to reset the PID with no success. The car can start if the G28 is unplugged and is running fine when it is connected, but still is experiencing intermittent misfires at higher RPM. The temperature sensor for the coolant (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 while the actual pressure is 0.0 when i rev the engine.

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

3. Fuel Pump

The fuel pump on the g28 is activated by a signal by the RPM sensor. The GM-style sensor is identical to the G4 and both are used in the 80, 100, 200, UrS and RS2 cars so you can easily find one at a junkyard or from a parts store. It is easy to test them: simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector's end facing up). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that needs to know the speed and position of the crankshaft to make a decision about timing of the fuel injector, for example. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these sensors go wrong, you will receive codes on the diagnostic scanner that can cause the engine to shut down.

Some of the signs of a malfunctioning G28 sensor include an inaccurate gearbox rev counter the gears are shifting faster than normal, and/or a misfire when you're in gear. It is probable that the sensor is failing and requires to be replaced if you notice any of these signs. They're cheap and easy to find, especially in the case of an Bosch model like ours. Alternatively, the GM version of this unit is also a good choice.

5. Tachometer

A malfunctioning engine speed sensor could be the cause of numerous issues in your car. It's a vital component of your audi connect key's transmission, as it sends information to the ECU about how fast or slow the car's crankshaft is spinning. If this sensor fails, it can affect the performance of the transmission, as well as the other car's components.

The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It sends an electrical signal through an uncolored wire to the ECU pin T55/49. The ECU is then able to process the signal to control fuel, timig and boost and then transmitting it to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by examining the continuity from the sensor to the tachometer. Also, 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 as well as pin T26a/12. You should see the resistance to be around 1000 ohms between these points. This is a typical part across the replacement audi key fob 80 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU, so the best ones might be availble in wrecking yards.