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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 on the outside of the transmission, above the flywheel gear. It transmits a signal to the ECU through an uncolored wire T55/49, then to the tachometer on the instrument cluster. 1. Engine Speed Sensor The grey wire is situated on the edge of transmission, just above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends an indicator 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 has to know when the crankshaft has reached TDC and also the position of the camshaft, in order to 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, possibly indicating the chain is stretched or a jump link on the upper chain of timing. The code won't appear without the additional information supplied 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 way to test it is to measure resistance between the sensor and the ECU. When the sensor is functional, it should read around 1000 ohms. If key for audi are having problems with this component, look for evidence of coolant or oil in the connector bay. 2. Injectors Yesterday accelerating full speed from highway paytoll, I experienced a big cut in power like the engine is running out of gas or the injectors aren't firing at all. Today, i pulled out the spark plugs. Three were soaked with gazoline and the 4th one was dry. I put tissue over each injector hole and when i turn the engine on without sparks, the 3 with gazoline jump out. The 4th one remains shut. I tried to test the ground connections of ECU pins 14,30, and 48/55. I found zero ohm. I'm assuming the issue is in another place. I also tried to reset PID but without success. The car can start if the G28 is disconnected and runs fine when it is connected, but still has the intermittent misfire issue at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is zero. I don't know what to do. I think I've all other possibilities out. But i'm worried that i might have missed something. Please let me know If you have any suggestions! TIA! 3. Fuel Pump The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style transmitter is identical to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. It is easy to find a spare in a wrecking shop or a parts store. It is simple to test them – just put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They should be infinite Ohms. 4. ECU Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that must know the speed and position of the crankshaft to make decisions regarding fuel injector timing etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these, the diagnostic scanner will show the codes that could trigger the engine shutting down. A failing G28 sensor can cause an inaccurate gearbox speed counter and a gearbox which shifts more quickly than normal, or an unfire when in gear. If you experience any of these problems, it is most likely that your sensor is failing and needs replacing. They are cheap and easy-to-find particularly if they're a Bosch model like ours. You can also choose the GM version of this unit is also a good choice. 5. Tachometer A faulty engine speed sensor could be the reason behind many issues with your vehicle. It's a vital component of your Audi's transmission, as it sends information to the ECU about how fast or slow the car's crankshaft is rotating. This sensor can cause the transmission to malfunction and other components in the car to be affected. The G5 engine speed sensor is located on the outside of the transmission, above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49, via a grey wire. The ECU uses this signal to control the flow of fuel and boost and also to timigrate. It also relays it to the G5 Tachometer inside the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. There should be an average resistance of 1000 ohms between these points. This is the same across the Audi 80-100-200-RS2 series, starting from the 1985 MC up to the 1997 UrS AN and the 1995 RS2 DU, so you might find good ones in wrecking yards.