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 situated at the top of the transmission just above the flywheel ring gear. It transmits a signal the ECU via the grey wire (T55/49) which is then sent to the tachometer within the instrument cluster.
1. Engine Speed Sensor
The grey wire is located at the edges of the transmission, above the flywheel ring. The sensor sends signals 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 signals to the G5 tachometer inside the instrument cluster.
The sensor is used to connect with the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft is TDC and the location of the camshaft so it can activate spark and injectors accordingly.
If this sensor fails when it fails, the ECU will display a P00160 error code. This indicates that the Crank Shaft is out of line with the Intake Camshaft. It could also indicate a chain stretch or a jump in the chain link of the upper chain. The code won't 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 each has its own functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. When the sensor is fully operational, it should read approximately 1000 ohms. Examine for signs of coolant or oil in the connector bay if you are experiencing problems with this part.
2. Injectors
Yesterday accelerating full speed from highway paytoll, i experienced massive power loss like the engine is running out of gas or the injectors aren't firing any more. I took out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was dry. I placed a tissue over each hole in the injector and when i start the engine without sparks, the three with gazoline jump right out. The 4th one stays closed. I checked the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. So i assume the problem is elsewhere.
I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it is running fine with the G28 plugged in. However, the intermittent misfire problem continues to occur at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature value of -49c, even if I unplug it. audi a1 key noticed that the gauge for oil pressure in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.
I'm not sure what to do. I believe that I've ruled everything else out. But i am afraid I might have missed something. Please let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. It is easy to find a spare in a wrecking shop or a parts store. It is easy to test them: simply switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector's end facing up). They must be infinite ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that needs to know the speed and position of the crankshaft in order to make decisions regarding fuel injector timing etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you have a problem with either one of these, the diagnostic scanner will display codes that could cause the engine shutting down.
A failing G28 sensor could result in an inaccurate gearbox speed counter, a gearbox that shifts more quickly than normal, or a misfire while in the gear. If you are experiencing any of these issues, it is likely that your sensor is going bad and requires replacement. They are cheap and easy-to-find particularly in the case of a Bosch sensor like ours. Alternately, GM's version this component is an excellent choice.
5. Tachometer
A malfunctioning engine speed sensor could be a cause for numerous problems in your car. It is a crucial part of your Audi's transmission, because it communicates to the ECU about how fast or slow the car's crankshaft is spinning. When this sensor fails, it will cause problems for the transmission as well as the other car's components.
The G5 engine speed sensor is located on the edge of the transmission just above the flywheel ring gear and sends a signal to the ECU at pin T55/49, via an uncolored wire. The ECU uses 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 test the sensor for failure by examining the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see around 1000 ohms of resistance between these two points. This is a standard 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 ones might be availble in wrecking yards.