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How to Replace an Audi G28 Engine Speed Sensor Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located at the top of the transmission, above the flywheel ring gear. It transmits a signal to the ECU via an uncolored 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 just above the flywheel ring gear, the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using a grey wire. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends an alert to the G5 Tachometer located in the instrument cluster. The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu must know when the crankshaft has reached TDC, and where the camshaft lies so that it can activate 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 aren't in sync and could indicate chain stretch or a jumped link on the upper timing chain. However the code will not be displayed on its own without additional information from other sensors (G4 and G40). Testing is a bit tricky because there are two connector pins and they have different functions but the most effective method to test it is to measure the resistance between the sensor and the ECU. When the sensor is fully functional, it should read about 1000 ohms. If you're having issues with this sensor, look for signs of coolant or oil in the connector bay. 2. Injectors Yesterday, as i was accelerating off the highway paytoll at maximum speed I noticed a massive drop in power. It was like the engine was running out of gas. Or my injectors were not firing. I pulled out the spark plugs this morning, three were drenched in gasoline and the 4th was dry. When audi replacement key start the engine without sparks i put tissue on the top of each of the injector holes and the 3 drenched with gazoline leap out, however the 4th stays closed. I checked the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. I assume that the problem is elsewhere. I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it is running fine with the G28 connected. However, the intermittent misfire problem continues to occur at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value that is -49c even after unplugging it. Also i noticed that the oil pressure gauge in the cockpit is showing 2 bar while the actual pressure is 0.0 when I crank up the engine. I'm not certain what to do, as i feel i have pretty much completely ruled out all other possibilities. However, i'm afraid that i might 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 sent by the RPM sensor. The GM-style sensor is the same as the G4 and both function in the 80 100 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or at 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 end facing up). audi spare key should be infinite ohms. 4. ECU The ECU in our 20vt turbo (3B AAN ABY ADU) engines must be aware of the position and speed of the crankshaft in order to make a decision about timing of the fuel injector, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you are experiencing issues with either one of these, the diagnostic scanner will show codes that could cause an engine shutdown. A malfunctioning G28 sensor can cause an inaccurate speed counter for the gearbox or a gearbox that shifts more quickly than normal, or a misfire in gear. It is possible that the sensor is failing and requires to be replaced if you encounter any of these symptoms. The good news is that they are quite affordable and easy to find, especially if you're looking at the Bosch sensor, like ours. Alternatively, GM's version of this part is an option. 5. Tachometer A failing engine sensor could cause a myriad of issues in your car. It's an essential component of the transmission of your Audi because it relays information to the ECU on how fast or slow the engine is spinning. If the sensor fails, it will disrupt the performance of the transmission and the rest of the car's components. The G5 engine speed sensor is situated on the outside of the transmission just above the flywheel ring gear and sends a signal to the ECU at pin T55/49 through an uncolored wire. The ECU then uses and processes this signal to regulate fuel, timig, and boost, and also sends it on to the G5 tachometer in the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. audi replacement keys should show around 1000 ohms of resistance between these two points. This is the same across the Audi 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS An and 1995 RS2 Du So, you may find some good ones in wrecking yards.