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How to Replace an Audi G28 Engine Speed Sensor Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. The sensor is located at the edge of transmission just above the flywheel gear. It sends a message to the ECU through a grey wire T55/49, then to the tachometer on the instrument cluster. 1. Engine Speed Sensor The grey wire is located on the outside of the transmission, above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU utilizes this information to control fuel and boost. It also sends signals to the G5 tachometer inside the instrument cluster. The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must 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 when it fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also be a sign of a chain stretch or a jumpy chain link in the upper chain. The code won't appear without the additional information provided by other sensors (G4 or G40). Testing can be a bit difficult as there are two different connector pins and they have different functions however the best method of testing it is to measure the resistance between the sensor and the ECU. It should read around 1000 ohms when it is in full operation. Check for evidence of coolant or oil in the connector bay if you are experiencing issues with this part. 2. Injectors Yesterday, while accelerating from the highway paytoll at full speed I noticed a significant reduction in power. It was like the engine was running out of gas. Or my injectors weren't firing. In the morning, i removed the spark plugs, 3 were soaked with gazoline and the 4th one was dry. I put tissue over each injector hole and when i start the engine with no sparks, the 3 with gazoline jump right out. The 4th one remains shut. I tested the ground connection of ECU pins 14,30 and 48/55. I got zero ohm. Therefore, i think the issue is somewhere else. I also tried to reset the PID without success. The car can start if the G28 is disconnected and runs fine when it is plugged in, but still has intermittent misfire issues at higher RPM. The temperature sensor for coolant (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 bar but the actual pressure is 0. I'm not certain what to do, i believe that i've eliminated everything else. But i am afraid I may have missed something. If anyone has suggestions, please chime in! TIA! 3. Fuel Pump The fuel pump in the g28 can be activated by a signal by the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily find an extra in a wrecking shop or parts store. It is simple to test them: simply switch your DMM into resistance mode and measure 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) engines needs to know both the position and speed the crankshaft in order to make a decision about timing of fuel injectors, etc. In order to do this it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these, the diagnostic scanner will display codes that could lead to an engine shutdown. Some of the symptoms of a malfunctioning G28 sensor are an inaccurate gearbox rev counter and gears that shift faster than normal, and/or a misfire when you are in gear. If you are experiencing any of these issues it is likely that your sensor is deteriorating and requires replacement. The good news is that they are quite affordable and easy to find, especially if you're looking at the Bosch model, which is what ours are. Alternatively, the GM version of this part is also a great option. 5. Tachometer A damaged engine sensor could cause a number of problems within your vehicle. It's an essential component of the transmission of your Audi, as it transmits information to the ECU about how fast or slow the engine is spinning. When this sensor fails, it will cause problems for the transmission and the rest of the 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 an uncolored wire to the ECU pin T55/49. new audi key uses this signal to regulate the amount of fuel and boost, and also to timigrate. It also relays it to the G5 Tachometer inside the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should detect the resistance to be around 1000 ohms between these two points. This is a typical component across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.