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How to Replace an Audi G28 Engine Speed Sensor In this video Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. The sensor is located at the top of the transmission, above the flywheel ring 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 grey wire is located at the edges of the transmission, just above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends signals to the G5 tachometer inside the instrument cluster. The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft reached TDC and also where the camshaft lies to trigger the spark and injectors. If this sensor fails the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync, possibly indicating the chain is stretched 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). It can be a bit difficult to test because there are several pins on the connector and each has its own functions. The best method for doing this is to measure the resistance between the ECU and the sensor. It should read approximately 1000 ohms when it is at full operation. Look for signs of coolant, or oil in the connector bay if you are experiencing issues with this component. 2. Injectors Yesterday, while accelerating at full speed from the highway paytoll, I experienced an abrupt drop in power like the engine is out of gas or injectors aren't firing any more. This morning i pull out the spark plugs, 3 were drenched with gazoline the 4th one was dry. I put tissue over each injector hole and when i turn the engine on without sparks, the three with gazoline jump right out. advanced key audi closed. I tested the ground connection of ECU pins 14,30 and 48/55. I found 0ohm. I'm assuming the issue is elsewhere. I also tried to reset the PID but with no luck. The car can start if the G28 is not plugged in and is running fine when it is connected, but still has intermittent misfire issues at higher RPM. The coolant sensor (G62), even when it is unplugged, shows temperatures of -49c. Also, i noticed that the oil pressure gauge in the cockpit is showing 2 bar while the actual pressure is 0.0 when i rev the engine. I'm not sure what to do, i feel i have pretty much completely ruled out all other possibilities. I'm worried that i might have missed something. If anyone has suggestions, please chime in! TIA! 3. Fuel Pump The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style sensor is the same as the G4 and both are used in the 80 100 200, UrS and RS2 cars so you can easily find one at a salvage yard or in a local parts store. It is easy to test them: simply switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing up). They should be infinite Ohms. 4. ECU The ECU of our 20vt turbo (3B AAN ABY ADU) engines needs to know the position and speed of the crankshaft in order to make a decision about timing of fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these goes bad you will get codes on the diagnostic scanner that can cause the engine to shut down. The signs of a malfunctioning G28 sensor are an inaccurate rev counter for the gearbox, gears shifting quicker than normal and/or a misfire when in gear. If you have any of these issues it is most likely that your sensor is failing and needs replacing. They're inexpensive and easy to locate, especially if they're a Bosch sensor like ours. Alternately, GM's version this component is an option. 5. Tachometer A failing engine speed sensor could be the cause of numerous issues in your car. It's a vital component of your Audi's transmission, because it communicates to the ECU about how fast or slow the vehicle's crankshaft is turning. If the sensor fails, it can disrupt the performance of the transmission and the other car's components. The G5 engine speed sensor is located on the edge of the transmission above the flywheel ring gear. It sends a signal to the ECU at pin T55/49, via an uncolored wire. The ECU then uses and processes this signal to control fuel, timig and boost, and also transmitting it to the G5 tachometer in the instrument cluster. You can check for sensor failure by examining the continuity of the sensor to the tachometer. Additionally, 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. It should show around 1000 ohms of resistance between these two points. This is a typical part across the Audi 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good ones could be available in wrecking yards.