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How to Replace an Audi G28 Engine Speed SensorCharles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is situated near the edges of the transmission, above the flywheel ring gear. It sends a message to the ECU through the grey wire T55/49 and then to the tachometer located on the instrument cluster.1. Engine Speed SensorThe sensor is located at the edge of the transmission just above the flywheel ring gear the G28 Engine Speed Sensor sends signals to ECU pin T55/49 via a grey wire. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends an indicator to the G5 Tachometer in instrument cluster.The sensor is used to correlate the G40 Camshaft position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC, and where the camshaft lies in order to activate the spark and injectors.If this sensor fails to function, the ECU will display an error code P00160. 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 jump in the chain link of the upper chain of timing. The code won’t show without the additional information provided by other sensors (G4 or G40).It is a little tricky to test since there are various connector pins, and they all have different functions. The best method for doing this is to measure the resistance between the ECU and the sensor. It should read around 1000 ohms if the sensor is in full operation. Check for evidence of coolant or oil in the connector bay if you are experiencing problems with this part.2. InjectorsYesterday, when i was accelerating to the fullest speed from highway paytoll i had a big cut in power as if the engine was running out of gas or injectors are not firing anymore. Today, i pulled out the spark plugs, three were drenched with gazoline the 4th one 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 fourth one remains closed. I checked the ground connection of ECU pins 14,30, and 48/55. I got 0ohm. I assume that the problem is somewhere else.I also tried to reset the PID without success. The car is able to start if the G28 is disconnected and it runs perfectly when it is plugged in, but still has intermittent misfire issues at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature of that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is 0.The Key Lab ‘m not sure what to do. I think I’ve eliminated everything else. I’m afraid i may have missed something. Please let me know If you have any suggestions! TIA!3. Fuel PumpThe fuel pump in the g28 is activated by a signal sent by the RPM sensor. The GM-style sensor is identical to the G4 and they both work 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: simply switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector’s end facing upwards). They should be infinite Ohms.4. ECUThe ECU in our 20vt turbo (3B AAN ABY ADU) engines must know both the speed and position of the crankshaft to determine timing of the fuel injector, etc. In order to do this it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go badly, you will see codes on the diagnostic scanner which could cause engine shut down.A damaged G28 sensor could result in an inaccurate speed counter for the gearbox or a gearbox that shifts faster than normal, or a misfire while in gear. If you have any of these problems, it is likely that your sensor is going bad and requires replacement. The good thing is that they are quite affordable and easily accessible, especially if you’re looking at an Bosch model, like ours. Alternatively, the GM version of this unit is also a good option.5. TachometerA failing engine sensor could cause a number of problems in your vehicle. It’s a vital component of the Audi’s transmission because it communicates to the ECU about how the car’s crankshaft is rotating. If the sensor fails, it can affect the performance of the transmission as well as the rest of the car’s components.The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It sends an electrical signal through gray wire to ECU pin T55/49. The ECU then processes this signal to control the flow of fuel, timig and boost, and also transmitting it to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by examining the continuity of 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 [79trace [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 common part that is found across the Audi 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU. Good ones might be availble in wrecking yards.