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. The 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 on the instrument cluster. 1. Engine Speed Sensor Located on the edge of the transmission just above the flywheel ring gear the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using a grey wire. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an indication to the G5 Tachometer within the instrument cluster. The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft reached TDC and also where the camshaft lies so that it can activate the spark and injectors. If this sensor fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is not in line with the Intake Camshaft. It could also indicate a chain stretch or a jumpy chain link in the upper timing chain. However the code will not appear 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 each one has different functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. It should read around 1000 ohms if the sensor is at full operation. Check for signs of coolant, or oil in the connector bay if there are issues with this part. 2. Injectors Yesterday, as i was accelerating off the highway paytoll at full speed, i noticed a huge reduction in power. It was like the engine was running out of gas. Or, my injectors were not firing. This morning i pull out the spark plugs. Three were drenched with gazoline the fourth one was dry. I put a piece of tissue over each injector hole and when i turn the engine on without sparks, the ones that have gazoline pop right out. The 4th one remains closed. I tried to test the ground connections of ECU pins 14,30, and 48/55. I got zero ohm. I think the issue is somewhere else. I also tried to reset PID without success. audi a3 key replacement can start if the G28 is unplugged and it runs perfectly when it is connected, but still has intermittent misfire issues at higher RPM. The coolant sensor (G62) even when unplugged, still shows a temperature of -49c. I also noticed that the oil pressure gauge in the cockpit shows 2 bar when the actual pressure is 0.0 when I crank up the engine. I don't know what to do. I think I've all other possibilities out. But i'm worried that I might have missed something. Let me know If you have any suggestions! TIA! 3. Fuel Pump The fuel pump in the g28 can be activated by a signal sent by the RPM sensor. The GM-style sender 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 at a parts store. Testing them is easy by putting your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black connector's side). They must be infinite Ohms. 4. ECU The ECU in our 20vt turbo (3B AAN ABY) engines must know both the speed and position of the crankshaft to determine timing of the fuel injector, etc. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes bad you will get codes on the diagnostic scanner that can cause the engine to shut down. The signs of a failed G28 sensor are an inaccurate rev counter in the gearbox, gears shifting quicker than normal and/or misfiring when you're in gear. If you experience any of these problems, it is likely that your sensor is going bad and should be replaced. They're cheap and easy to find especially in the case of an Bosch model like ours. Alternatively, the GM version of this part is also a good choice. 5. Tachometer A malfunctioning engine speed sensor could be the reason behind numerous problems in your car. It's an essential component of the transmission in your Audi since it sends information to the ECU on how fast or slowly the engine is spinning. When this sensor fails, it could affect the performance of the transmission, as well as the other car's components. The G5 engine speed sensor is located on the edge of the transmission, above the flywheel ring gear. It sends a signal to the ECU at pin T55/49 via a grey wire. The ECU is then able to process this signal to control the flow of fuel, timig and boost, and also sends it on to the G5 Tachometer located in the instrument cluster. You can check the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. It should show approximately 1000 ohms of resistance between those two pins. This is a typical part across the Audi 80 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.
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