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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 situated at the top of the transmission just above the flywheel ring gear. It transmits a signal to the ECU through an uncolored wire T55/49, then to the tachometer on the instrument cluster. 1. Engine Speed Sensor Located on the edge of the transmission, above the flywheel ring gear, the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via an uncolored wire. The ECU utilizes this information to regulate the amount of fuel and boost. It also sends an indicator to the G5 Tachometer in instrument cluster. The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC and also the location of the camshaft 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 are out of sync, possibly indicating chain stretch or a jumped link on the upper chain of timing. However the code will not be displayed on its own without additional information from other sensors (G4 and G40). It's a bit tricky to test as there are different 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. When the sensor is fully operational, it should be reading around 1000 ohms. Examine for evidence of coolant or oil in the connector bay if there are problems with this part. 2. Injectors Yesterday, when accelerating from highway paytoll at full speed I noticed a significant decrease in power. It was like the engine had run out of gas. Or my injectors were not firing. I took out the spark plugs this morning and found that 3 were soaked with gasoline and the fourth was dry. When i crank the engine without sparks, I put a piece of tissue on the top of each of the injector holes and the 3 drenched with gazoline leap out, however the 4th one stays shut. I tested the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got zero ohm. I think the issue is in another location. I also tried to reset PID but without success. The car is able to start if the G28 is unplugged and is running fine when it is plugged in but it still is experiencing intermittent misfires at higher RPM. The coolant sensor (G62), even when it is unplugged, shows an ice temperature of -49c. Also, i noticed that the gauge for oil pressure in the cockpit shows 2 bar while the actual pressure is 0.0 when I crank up the engine. I'm not sure what to do, as i think i've pretty much eliminated everything else. I'm afraid i may have missed something. Please let replacement audi key thekeylab.co.uk know if you have any ideas! TIA! 3. Fuel Pump The fuel pump in the g28 can be activated by a signal from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily locate a spare in a wrecking shop or a parts store. It is simple to test them – just put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They must be infinite ohms. 4. ECU The ECU of our 20vt turbo (3B AAN ABY ADU) engines requires to be aware of the position and speed of the crankshaft in order to make a decision about timing of fuel injectors, etc. In order to do this it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either one of these, the diagnostic scanner will show the codes that could trigger an engine shutdown. A malfunctioning G28 sensor can cause an inaccurate speed counter for the gearbox or a gearbox that shifts faster than normal, or a misfire in the gear. It is likely that your sensor is failing and needs to be replaced if you experience any of these symptoms. The good news is that they are very affordable and easily accessible, especially when you're looking at an Bosch model, like ours. Alternatively, GM's version of this component is an option. 5. Tachometer A failing engine sensor could cause a variety of issues in your vehicle. It's a crucial component of the transmission of your Audi since it sends information to the ECU regarding how fast or slowly the car's engine is turning. If the sensor fails, it could affect the performance of the transmission and the other car's components. The G5 engine speed sensor is situated on the edge of the transmission just 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 regulate fuel, timig, and boost, and also transmitting it to the G5 tachometer in the instrument cluster. You can test the sensor for failure by checking continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. It should show approximately 1000 ohms of resistance between these two points. This is the same across the Audi 80-100-200-RS2 series, starting from the 1985 MC up to the 1997 UrS An and 1995 RS2 Du, so you might find some good ones in wrecking yards.