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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 located on the edge of the transmission, above the flywheel ring gear. It sends a message to the ECU through an uncolored wire T55/49, then to the tachometer in the instrument cluster. 1. Engine Speed Sensor The grey wire is located on the outside of the transmission, directly above the flywheel ring. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster. The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft has reached TDC, and the location of the camshaft in order to 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 chain of timing. However, the code won't be displayed on its own without additional information from other sensors (G4 and G40). Testing can be a bit difficult since there are two pins for the connector and they perform different functions but the best method of testing it is by measuring resistance between the sensor and the ECU. If the sensor is operational, it should be reading approximately 1000 ohms. Examine for evidence of coolant or oil in the connector bay if there are issues with this component. 2. Injectors Yesterday, when i was accelerating to the fullest speed from highway paytoll i had a big cut in power as if the engine was running out of gas or injectors are not firing at all. I took out the spark plugs this morning and found that 3 were soaked with gasoline and the 4th was dry. When I crank the engine, there are no sparks i put tissue on the top of each hole in the injector, the 3 drenched with gazoline pop out, but the 4th one stays shut. I tested the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. So i assume the problem is elsewhere. I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it runs fine with the G28 connected. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0. I'm not certain what to do, i think i've pretty much eliminated everything else. But i'm worried that I might have missed something. If anyone has suggestions, please chime in! TIA! 3. Fuel Pump The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style sensor is the same as the G4 and both function in the 80, 100, 200, UrS and RS2 cars so you can easily find one at a junkyard or at a parts store. It is simple to test them to do – just put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's end). They should be infinite ohms. 4. ECU Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that has to be aware of the speed and position of the crankshaft to make decisions about timing of the fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you have a problem with either one of these, the diagnostic scanner will display codes that could cause an engine shut down. A failing G28 sensor could result in an inaccurate gearbox speed counter and a gearbox which shifts more quickly than normal, and/or a misfire in gear. If you experience any of these problems, it is most likely that your sensor is going bad and should be replaced. They're inexpensive and easy to locate particularly if they're a Bosch unit like ours. Alternately, GM's version this component is a good option. 5. Tachometer A malfunctioning engine sensor can cause a number of problems in 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 car's crankshaft is turning. If the sensor fails, it will cause problems for the transmission and the rest of the car's components. The G5 engine speed sensor is situated on the outside 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 utilizes this signal to control the flow of fuel and boost and also timig. It also transmits it to the G5 Tachometer inside the instrument cluster. The Keylab can check for sensor failure by examining the continuity from the sensor to the tachometer. Also, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 as well as pin T26a/12. You should see a resistance of approximately 1000 ohms between these two points. This is a standard 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 so good ones might be availble in wrecking yards.