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How to Replace an Audi G28 Engine Speed Sensor In this video, Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is situated at the edge of transmission over the flywheel gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer on the instrument cluster. 1. Engine Speed Sensor The sensor is located at the edge of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 through the grey wire. lost audi key utilizes this information to regulate the flow of fuel, timig and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster. The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC, and where the camshaft lies to trigger 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 the chain stretching or a jump link on the upper timing chain. The code won't appear without the additional information provided by other sensors (G4 or G40). Testing is a bit challenging because there are two connector pins and they have different functions but the best method to test it is to measure the resistance between the sensor and the ECU. It should read about 1000 ohms when the sensor is at full operation. If you're having issues with this part, check for signs of oil or coolant in the connector bay. 2. Injectors Yesterday accelerating full speed from highway paytoll i had an abrupt drop in power like the engine is out of gas or injectors are not firing at all. I took out the spark plugs this morning and found that 3 were soaked in gasoline, and the fourth was unclean. When i crank the engine without sparks i put tissue on the top of each of the injector holes and the 3 that were drenched in gazoline leap out, however the 4th stay shut. I tried to test the ground connections of ECU pins 14,30, and 48/55. I got zero ohm. So i assume the problem is somewhere else. I also tried to reset the PID but without success. The car will start if the G28 is not plugged in and runs fine 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. Also i noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when I crank up the engine. I'm not sure what to do, as i think i've pretty much ruled out everything else. But i'm worried that I may have missed something. Let me know if you have any ideas! TIA! 3. Fuel Pump The fuel pump in the g28 receives signals from 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 at a parts store. It is simple to test them – just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They should be infinite Ohms. 4. ECU The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to know the position and speed the crankshaft to make decisions regarding timing of fuel injectors, etc. To accomplish this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these sensors, the diagnostic scanner will display codes that could cause an engine shutdown. Some of the signs of a malfunctioning G28 sensor are an inaccurate rev counter in the gearbox the gears are shifting faster than normal and/or a misfire when in gear. It is likely that the sensor is failing and needs to be replaced if you encounter any of these symptoms. The good thing is that they are very cheap and easy to find particularly in the case of an Bosch model, which is what ours are. You can also choose the GM version of this component is also a good option. 5. Tachometer A damaged engine sensor could cause a myriad of issues in your vehicle. It's a crucial component of the transmission of your Audi, as it transmits information to the ECU about how fast or slow the engine is turning. If the sensor fails, it could affect the performance of the transmission and the other car's components. The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It transmits signals via an uncolored wire to the ECU pin T55/49. The ECU utilizes this signal to regulate fuel and boost, as well as timig. It also relays it to the G5 Tachometer located in the instrument cluster. You can check for sensor failure by examining the continuity of the sensor to the tachometer. You can also examine the continuity between pins 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 approximately 1000 ohms resistance between those points. This is a standard component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best ones could be available in wrecking yards.