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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, above the flywheel gear. It sends a message to the ECU through the grey wire T55/49 and then to the tachometer on the instrument cluster. 1. Engine Speed Sensor The grey wire is located on the outside of the transmission, just above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU utilizes this information to regulate boost and fuel. It also sends a signal to the G5 tachometer inside the instrument cluster. The sensor is used to connect the G40 Camshaft position Sensor. The ecu has to know when the crankshaft reached TDC, and where the camshaft lies so that it can activate the spark and injectors. If this sensor fails the ECU will display 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. The code will not appear without the additional information provided by other sensors (G4 or G40). It is a little tricky to test because there are different connector pins, and each has its own functions. The best way to do it is by measuring the resistance between the ECU and the sensor. It should read about 1000 ohms when it is operating at its maximum. If you're experiencing issues with this component, look for evidence of coolant or oil in the connector bay. 2. Injectors Yesterday, while accelerating from the highway paytoll at maximum speed I noticed a significant drop in power. It was like the engine was running out of gas. Or, my injectors were not firing. In the morning, i removed the spark plugs. Three were soaked with gazoline and the fourth one was dry. When i crank the engine, there are no sparks i put tissue on the top of each of the injector holes, the 3 drenched with gazoline jump out but the 4th stay shut. I checked the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. So i assume the problem is elsewhere. I also tried to reset PID without success. The car can start when the G28 is not plugged in and it runs perfectly when it is connected, but still has intermittent misfire issues at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of -49c, even if I unplug it. Also, i noticed that the oil pressure gauge in the cockpit shows 2 bar while the actual pressure is 0.0 when I crank up the engine. I'm not sure what to do. I think I've eliminated everything else. I'm concerned that i may 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 by the RPM sensor. The GM-style transmitter is similar to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily locate a spare in a wrecking shop or a parts store. Testing them is easy to do – just put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black connector's side). They should be infinite Ohms. 4. ECU The ECU of our 20vt turbo (3B AAN ABY) engines needs to know the speed and position of the crankshaft to determine timing of the fuel injector, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these goes badly, you will see codes on the diagnostic scanner that can cause the engine to shut down. The signs of a failing G28 sensor include an inaccurate rev counter for the gearbox, gears shifting quicker than normal, and/or a misfire when in gear. It is probable that your sensor is failing and requires to be replaced if you experience any of these symptoms. They're inexpensive and easy to locate especially when they're a Bosch sensor like ours. Alternately, GM's version this part would be an excellent choice. 5. Tachometer A malfunctioning engine speed sensor could be the reason behind a slew of issues with your car. It's a vital component of the Audi's transmission since it relays information to the ECU about how fast or slow the vehicle's crankshaft is spinning. When this sensor fails, it could cause problems for the transmission and the rest of the car's components. The G5 engine speed sensor is located on the outside of the transmission just above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 via an uncolored wire. The ECU then uses and processes the signal to control the flow of fuel, timig and boost and then sends it on to the G5 tachometer inside the instrument cluster. car key replacement audi can determine if the sensor is in failure by examining the continuity of the sensor to the tachometer. Also, you can 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. You should see approximately 1000 ohms of 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 good ones might be availble in wrecking yards.