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. The sensor is situated at the top of the transmission just above the flywheel ring gear. It transmits a signal to the ECU via the grey wire T55/49 and then to the tachometer on the instrument cluster. 1. Engine Speed Sensor The grey wire is situated at the edges of the transmission, just above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU utilizes this information to control boost and fuel. It also sends an indication to the G5 Tachometer located in the instrument cluster. The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must be aware of when the crankshaft has reached TDC and also where the camshaft lies in order to activate the spark and injectors. If this sensor fails to function, the ECU will display a P00160 error message. This indicates that the Crank Shaft is out of line with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumped chain link in the upper timing chain. The code won't show without the additional information provided by other sensors (G4 or G40). Testing is a bit tricky as there are two different connector pins, and they serve different purposes but the best method to test it is to measure resistance between the sensor and the ECU. If the sensor is operational, it should read around 1000 ohms. Look for evidence of coolant or oil in the connector bay if you are experiencing problems with this part. 2. Injectors Yesterday, as i was accelerating off the highway paytoll at a high speed, i noticed a huge reduction in power. It was as if 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 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 on ECU pins 14/55,30/55 and 48/55 I got zero ohm. I think the issue is somewhere else. I also tried to reset PID but without success. The car will start when the G28 is unplugged, and it runs fine with the G28 connected. However the intermittent misfire issue persists at higher RPM. https://graydesk4.bravejournal.net/10-facts-about-audi-car-key-replacement-that-make-you-feel-instantly-an (G62) even when it is unplugged, shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is 0. I'm not certain what to do, but i think i've pretty much ruled out everything else. But i am afraid I may 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 by the RPM sensor. The GM-style sender 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 junkyard or at a parts store. It is simple to test them - 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 end). They should be infinite ohms. 4. ECU The ECU of our 20vt turbo (3B AAN ABY) engines must be aware of the position and speed the crankshaft in order to make a decision about fuel injector timing, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you encounter a problem with either of these sensors, the diagnostic scanner will display codes that could cause an engine shut down. The signs of a failing G28 sensor are an inaccurate rev counter in the gearbox and gears that shift faster than normal and/or misfiring when you are in gear. It is likely that your sensor is failing and needs to be replaced if you notice any of these signs. They're inexpensive and easy to locate especially if they're a Bosch sensor like ours. 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 an essential component of the Audi's transmission since it relays information to the ECU about how fast or slow the vehicle's crankshaft is turning. If this sensor fails, it will disrupt the performance of the transmission and the rest of the car's components. The G5 engine speed sensor is located on the outside of the transmission above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU is then able to process the signal to control fuel, timig, and boost and then sends it on to the G5 Tachometer located in the instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. It should show around 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 through the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.