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How to Replace an Audi G28 Engine Speed Sensor Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. The sensor is situated at the top of the transmission above the flywheel ring gear. It sends a signal to the ECU via the grey wire (T55/49) and then to the tachometer located in the instrument cluster. 1. Engine Speed Sensor It is located on the outside of the transmission above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through an uncolored wire. The ECU then uses this information to control fuel, timig and boost. It also sends an indication to the G5 Tachometer within the instrument cluster. The sensor is used to link the G40 Camshaft position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is located so that it can trigger spark and injectors in the right way. If this sensor fails, the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync, possibly indicating the chain is stretched or a jump link on the upper chain of timing. The code will not appear without the additional information provided by other sensors (G4 or G40). It is a little tricky to test as there are different pins on the connector, and they all have different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. When how to open audi car key is operational, it should read approximately 1000 ohms. Check for evidence of coolant or oil in the connector bay if you are experiencing issues with this component. 2. Injectors Yesterday, when accelerating from highway paytoll at maximum speed, i noticed a huge drop in power. It was like the engine had run out of gas. Or, my injectors were not firing. I pulled out the spark plugs this morning, three were soaked in gasoline, and the 4th was dry. When i crank the engine without sparks i put tissue on the top of each of the injector holes, the 3 drenched with gazoline jump out but the 4th stays closed. I checked the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. So i assume the problem is somewhere else. I also tried to reset the PID with no success. The car is able to start if the G28 is disconnected and it runs perfectly when it is plugged in however it has intermittent misfire issues at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature value of -49c, even if I unplug it. I also noticed that the gauge for oil pressure in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when i rev the engine. I'm not certain what to do, i think i've pretty much eliminated everything else. I'm worried that i might have missed something. Let me know should you have any suggestions! TIA! 3. Fuel Pump The fuel pump in the g28 is activated by a signal sent from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find an extra in a wrecking shop or a parts store. Testing them is easy – put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black end of the connector). They must be infinite Ohms. 4. ECU The ECU in our 20vt turbo (3B AAN ABY) engines requires to be aware of the speed and position of the crankshaft to make decisions regarding timing of the fuel injector, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go wrong, you will receive codes on the diagnostic scanner which could cause engine shut down. Some of the signs of a failing G28 sensor are an inaccurate gearbox rev counter and gears that shift faster than normal and/or misfiring when you are in gear. If you have any of these issues, it is most likely that your sensor is failing and requires replacement. They're cheap and easy to find particularly when they're a Bosch model like ours. Alternately, GM's version this component is a good option. 5. Tachometer A faulty engine speed sensor could be a cause for many issues with your car. It is an important part of the transmission of your Audi since it sends information to the ECU about how fast or slow 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 speed sensor is located on the edge of the transmission above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 through a grey wire. The ECU then uses and processes this signal to regulate fuel, timig and boost and then transmitting 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 to pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should detect the resistance to be around 1000 ohms between these two points. This is a common feature across the Audi 80-100-200-RS2 range, beginning with the 1985 MC and up to the 1997 UrS AN and 1995 RS2 Du, so you might find them in wrecking yards.