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How to Replace an Audi G28 Engine Speed Sensor Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located near the edges of the transmission, above the flywheel ring gear. It sends a signal to the ECU via an uncolored wire (T55/49) which is then sent to the tachometer within the instrument cluster. 1. Engine Speed Sensor The grey wire is located on the edge of transmission, 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 the flow of fuel, timig and boost. It also sends a signal to the G5 tachometer in the instrument cluster. The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu has to be aware of 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 throw the P00160 error, which means the Crank Shaft and Intake Camshaft are not in sync and could indicate the chain is stretched or a jump link on the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40). It's a bit tricky to test as there are different connector pins, and each one has different functions. The best way to do it is to measure the resistance between the ECU and the sensor. If the sensor is operational, it should be reading approximately 1000 ohms. Examine for signs of coolant, or oil in the connector bay if you have problems with this part. 2. Injectors Yesterday, as i was accelerating off the highway paytoll at full speed, i noticed a huge decrease in power. It was like the engine was running out of gas. Or my injectors weren't firing. I took out the spark plugs this morning, 3 were drenched in gasoline and the fourth was unclean. I placed a tissue over each injector hole, and when i start the engine without sparks, the ones with gazoline jump out. The 4th one stays shut. I tested the ground connection of ECU pins 14,30, and 48/55. I got 0ohm. Therefore, i think the issue is somewhere else. I also tried to reset the PID but without success. The car can start when the G28 is unplugged and it runs perfectly when it is connected but it still has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even when unplugged, still shows an ice temperature of -49c. Also i noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when i rev the engine. I'm not sure what to do, as i think i've pretty much ruled out everything else. But i am afraid i might have missed something. Let me know if you have any ideas! TIA! 3. Fuel Pump The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style sensor is identical to the G4 and they both work in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or in a local parts store. Test them out – put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's end). They must be infinite Ohms. 4. ECU The ECU of our 20vt turbo (3B AAN ABY) engines requires to be aware of the position and speed the crankshaft in order to make a decision about fuel injector timing, etc. To accomplish this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go badly, you will see codes on the diagnostic scanner which could cause engine shut down. The signs of a failed G28 sensor are an inaccurate gearbox rev counter and gears that shift faster than normal and/or a misfire when you are in gear. If you are experiencing any of these issues, it is likely your sensor is deteriorating and needs replacing. They're cheap and easy to find especially if they're a Bosch unit like ours. Alternatively, GM's version of this part is an excellent choice. 5. Tachometer A malfunctioning engine speed sensor could be a cause for a slew of issues with your vehicle. It's a vital component of your Audi's transmission, since it relays information to the ECU about how fast or slow the vehicle's crankshaft is rotating. If this sensor fails, it can affect the performance of the transmission as well as the rest of the car's components. The G5 engine speed sensor is located at the outside of the transmission just above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49, via a grey wire. The ECU then processes the signal to control the flow of fuel, timig and boost and then transmitting it to the G5 tachometer inside the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer. You can also check continuity 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. audi a4 key replacement should detect a resistance of approximately 1000 ohms between these two points. This is the same across the Audi 80-100-200-RS2 model, ranging from the 1985 MC up to the 1997 UrS AN and 1995 RS2 DU, so you might find them in wrecking yards.