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 near the transmission's edge just above the flywheel gear. It sends a signal to the ECU via the grey wire (T55/49) and then to the tachometer 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 signals to ECU pin T55/49 through a grey wire. The ECU utilizes this information to control boost and fuel. It also sends a signal to the G5 Tachometer located in the instrument cluster.
The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft has reached TDC, and where the camshaft lies so that it can activate the spark and injectors.
If this sensor fails to function, the ECU will display a P00160 error message. This means that the Crank Shaft is out of line with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumpy chain link in the upper timing chain. However audi car key will not appear on its own, without additional information from other sensors (G4 and G40).
It can be a bit difficult to test since there are various 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. When the sensor is fully operational, it should read about 1000 ohms. If you're having issues with this part, check for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday accelerating full speed from highway paytoll i had massive power loss like the engine is out of gas or injectors aren't firing any more. In the morning, i removed the spark plugs, 3 were drenched in gazoline, the fourth was dry. When i crank the engine with no sparks, I put a piece of tissue on top of each injector hole and the 3 drenched with gazoline jump out but the 4th stays shut. I checked the ground connection of ECU pins 14,30, and 48/55. I got 0ohm. I'm assuming the issue is elsewhere.
I also tried to reset PID without success. The car will start when the G28 is disconnected and runs fine when it is connected, but still has the intermittent misfire issue at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature value of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is zero.
I'm not sure what to do, i think i've pretty much eliminated everything else. However, i'm afraid that I might have missed something. Let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style transmitter is the same as the G4 and both function in the 80, 100 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or at a parts store. It is simple to test them by putting 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 end of the connector). They should 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 the crankshaft in order to make a decision about timing of fuel injectors, etc. To do this, it uses 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 that can cause the engine to shut down.
A failing G28 sensor can cause an inaccurate gearbox speed counter or a gearbox that shifts faster than normal, or an unfire when in the gear. It is likely that your sensor is failing and requires to be replaced if you notice any of these symptoms. They're inexpensive and easy to locate, especially in the case of a Bosch sensor like ours. If you prefer, GM's version of this component is an excellent choice.
5. Tachometer
A failing engine sensor could cause a number of problems within your vehicle. It is a crucial part of the Audi's transmission as it sends information to the ECU about how the car's crankshaft is turning. If the sensor fails, it will cause problems for the transmission as well as the rest of the car's components.
The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It transmits a signal via gray wire to ECU pin T55/49. The ECU utilizes this signal to control the amount of fuel and boost, as well as timig. It also relays it to the G5 Tachometer located in 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 on pin T6a/1 (trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. There should be a resistance of approximately 1000 ohms between these two points. This is a typical component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.