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How to Replace an Audi G28 Engine Speed Sensor Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is situated near the edges of the transmission, above the flywheel ring gear. It sends a signal to the ECU via an uncolored wire (T55/49) and then to the tachometer in the instrument cluster. 1. Engine Speed Sensor The grey wire is located on the outside of the transmission, just above the flywheel ring. This sensor sends signals through the grey wire to pin T55/49. The ECU then uses this information to control fuel, timig and boost. It also sends signals to the G5 Tachometer located in the instrument cluster. The sensor is used to connect the G40 Camshaft position Sensor. The ecu has to know when the crankshaft has reached TDC, and where the camshaft lies in order to activate 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 aren't in sync, possibly indicating the chain is stretched or a jump link on the upper timing chain. However, the code won't appear on its own, without additional information from other sensors (G4 and G40). Testing is a bit tricky as there are two different pins for the connector and they serve different purposes but the best way to test it is by measuring resistance between the sensor and the ECU. It should read around 1000 ohms when the sensor is in full operation. Look for lost audi keys of coolant, or oil in the connector bay if there are issues with this part. 2. Injectors Yesterday accelerating full speed from highway paytoll, I experienced an abrupt drop in power like the engine is out of gas or injectors aren't firing at all. This morning i pull out the spark plugs. Three were soaked with gazoline and the 4th one was dry. When I crank the engine without sparks i put tissue on top of each injector hole and the 3 that were drenched in gazoline leap out, however the 4th stay shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found zero ohm. I'm assuming that the issue is elsewhere. I also tried to reset the PID but with no luck. The car will start when the G28 is disconnected, but it runs fine with the G28 plugged in. However the intermittent misfire issue persists at higher RPM. The coolant sensor (G62) even when unplugged, still shows temperatures of -49c. Also i noticed that the gauge for oil pressure in the cockpit is showing 2 bar when the actual pressure is 0.0 when I crank up the engine. I'm not certain what to do, i think i've pretty much completely ruled out all other possibilities. But i am afraid I might have missed something. Please let me know If you have any suggestions! TIA! 3. Fuel Pump The fuel pump in the g28 is activated by a signal from the RPM sensor. The GM-style sensor is the same as the G4 and they both work in the 80, 100 200, UrS and RS2 cars so you can easily find one at a wrecking yard or in a local parts store. It is simple to test them – just switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite Ohms. 4. ECU The ECU in our 20vt turbo (3B AAN ABY ADU) engines must know both the position and speed the crankshaft in order to make a decision about fuel injector timing, etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If lost audi key of these goes bad you will get codes on the diagnostic scanner which can lead to engine shutdown. Some of the symptoms of a failing G28 sensor are an inaccurate rev counter in the gearbox, gears shifting quicker than normal, and/or a misfire when in gear. If you are experiencing any of these problems, it is most likely that your sensor is deteriorating and requires replacement. They're cheap and easy to find especially in the case of a Bosch unit like ours. Alternatively, the GM version of this component is also a good choice. 5. Tachometer A faulty engine speed sensor could be the cause of many issues in your car. It is an important part of the transmission of your Audi, as it transmits information to the ECU on how fast or slowly the car's engine is spinning. This sensor can cause the transmission to malfunction and other components in the car to be affected. The G5 engine sensor is located near the edge of transmission, above the flywheel ring. It transmits signals via an uncolored wire to the ECU pin T55/49. The ECU utilizes this signal to control fuel and boost, and also to timigrate. It also relays it to the G5 Tachometer located in the instrument cluster. You can determine if the sensor is in 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 [79trace [79]) and between pin T6a/1 and pin T26a/12. There should be the resistance to be around 1000 ohms between these two points. This is a standard part 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.