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How to Replace an audi a3 key G28 Engine Speed Sensor

In this video, Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is located at the edge of transmission, above the flywheel gear. It transmits a signal to the ECU via the grey wire T55/49 and 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 G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through an uncolored wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends signals to the G5 Tachometer located in the instrument cluster.

The sensor is used to correlate the G40 Camshaft position Sensor. The ecu must be aware of when the crankshaft has reached TDC and also where the camshaft lies to trigger the spark and injectors.

If this sensor fails the ECU will display the P00160 error, which means the Crank Shaft and Intake Camshaft are not in sync and possibly indicating chain stretch or a jumped link on 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 different connector pins, and each one has different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. It should read around 1000 ohms when it is operating at its maximum. Look for signs of coolant, or oil in the connector bay if there are issues with this component.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll i had a big cut in power like the engine is out of gas or the injectors are not firing at all. In the morning, i removed the spark plugs, 3 were soaked with gazoline and the fourth one was dry. When i crank the engine with no sparks, I put a piece of tissue on the top of each of the injector holes, the 3 drenched with gazoline jump out but the 4th stays closed. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 i get zero Ohm. Therefore, i think the issue is in another place.

I also tried to reset PID but without success. The car can start if the G28 is unplugged and it runs perfectly when it is connected however it has the intermittent misfire issue at higher RPM. The coolant sensor (G62), even when unplugged, still shows temperatures of -49c. I also noticed that the oil pressure gauge in the cockpit is showing 2 bar while the actual pressure is 0.0 if i crank up the engine.

I'm not certain what to do, as i feel i have pretty much eliminated everything else. But i am afraid i might have missed something. Let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump on the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter is identical to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. It is easy to find the spare in a salvage shop or a parts store. It is simple to test them by putting your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's end). They should 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. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either one of these, the diagnostic scanner will display codes that could cause the engine shutting down.

Some of the signs of a failing G28 sensor are an inaccurate rev counter in the gearbox the gears are shifting faster than normal and/or misfiring when you are in gear. If you are experiencing any of these problems, it is most likely that your sensor is going bad and requires replacement. The good thing is that they are very affordable and easily accessible, especially if you're looking at a Bosch model, like ours. If you prefer, GM's version of this part is a good option.

5. Tachometer

A malfunctioning engine speed sensor could be the reason behind a slew of problems in your car. It's an essential component of the transmission of your audi remote key since it sends information to the ECU on how fast or slow the engine of the car is turning. If the sensor fails, it can 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 edge of the transmission, above the flywheel ring gear and transmits a signal to the ECU at pin T55/49, via a grey wire. The ECU uses this signal to regulate the flow of fuel and boost and also timig. It also sends it to the G5 Tachometer inside the instrument cluster. You can check for sensor failure by examining the continuity of the sensor to the tachometer. You can also check 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. There should be the resistance to be around 1000 ohms between these points. This is a common component across the audi key fob not working 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.