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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 on the edge of the transmission above the flywheel ring gear. It sends a message to the ECU via the grey wire T55/49 and then to the tachometer located on the instrument cluster. 1. Engine Speed Sensor The grey wire is located at the edges of the transmission, directly above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU utilizes this information to control the amount of fuel and boost. It also sends an indication to the G5 tachometer inside the instrument cluster. The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft has reached TDC and also the location of the camshaft to trigger the spark and injectors. If this sensor fails the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync, possibly indicating chain stretch or a jumped link on the upper chain of timing. The code won't appear without the additional information provided by other sensors (G4 or G40). It is a little tricky to test as there are several connector pins, and they all have different functions. The best way to do it is to measure the resistance between the ECU and the sensor. It should read about 1000 ohms when it is at full operation. Check for signs of coolant, or oil in the connector bay if you are experiencing issues with this component. 2. Injectors Yesterday, while accelerating from the highway paytoll at full speed, i noticed a huge reduction in power. It was as if the engine had run out of gas. Or, my injectors were not firing. In the morning, i removed the spark plugs, three were soaked with gazoline and the 4th one was dry. When I crank the engine with no sparks, I put a piece of tissue on top of each injector hole, the 3 drenched with gazoline jump out but the 4th stays shut. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. I get zero Ohm. I assume that the problem is somewhere else. I also tried to reset the PID without success. The car will start when the G28 is disconnected, but it runs fine with the G28 plugged in. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62), even when unplugged, still shows temperatures of -49c. Also, This Web-site noticed that the oil pressure gauge in the cockpit is showing 2 bar when the actual pressure is 0.0 when i rev the engine. I don't know what to do. I believe that I've eliminated everything else. I'm afraid i may have missed something. Let me know should you have any suggestions! TIA! 3. Fuel Pump The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. It is easy to find the spare in a salvage shop or parts store. It is simple to test them to do – just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from the left on the black end of the connector). They should be infinite Ohms. 4. ECU The ECU of our 20vt turbo (3B AAN ABY ADU) engines needs to know both the speed and position of the crankshaft in order to make a decision about fuel injector timing, etc. To accomplish this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes wrong, you will receive codes on the diagnostic scanner which could cause engine shut down. Some of the signs of a failed G28 sensor are an inaccurate rev counter in the gearbox the gears are shifting faster than normal, and/or a misfire when you're in gear. If you have any of these problems, it is likely that your sensor is deteriorating and should be replaced. 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 part is also a good option. 5. Tachometer A failing engine sensor could cause a number of problems in your car. It is a crucial part of the Audi's transmission because it communicates to the ECU about how the car's crankshaft is rotating. 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 edge of the transmission above the flywheel ring gear. It sends a signal to the ECU at pin T55/49, via a grey wire. The ECU is then able to process the signal to control fuel, timig, and boost as well as sends it on 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 T6a/1 and the instrument cluster pin T26a/12. You should detect a resistance of approximately 1000 ohms between these two points. This is a typical part that is found across the Audi 80, 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good ones could be available in wrecking yards.