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. This sensor is located on the outside of the transmission just above the flywheel gear. It transmits a signal to the ECU via an uncolored wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the outside of the transmission, just above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then uses this information to control the boost, fuel, and timig. It also sends an indication to the G5 Tachometer located in the instrument cluster.
The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu has to know when the crankshaft reached TDC and also the location of the camshaft so that it can activate the spark and injectors.
If this sensor fails, the ECU will throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync, possibly indicating chain stretch or a jumped link on the upper chain of timing. However the code will not appear on its own, without additional information from other sensors (G4 and G40).
Testing is a bit tricky as there are two different pins for the connector and they have different functions but the best method of testing it is to measure the resistance between the sensor and the ECU. When the sensor is fully functional, it should read approximately 1000 ohms. Check for signs of coolant or oil in the connector bay if you have problems with this part.
2. Injectors
Yesterday, when i was accelerating to the fullest speed from highway paytoll, I experienced a big cut in power as if the engine was running out of gas or injectors are not firing anymore. I pulled out the spark plugs this morning, 3 were soaked with gasoline and the fourth was dry. I put tissue over each hole in the injector and when I start the engine without sparks, the 3 with gazoline jump out. The 4th one remains shut. I checked the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ i get zero ohm. Therefore, i think the issue is in another place.
I also tried to reset the PID without success. The car can start when the G28 is disconnected and is running fine when it is connected, but still has the intermittent misfire issue at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature of that is -49c even after unplugging it. Also, i noticed that the oil pressure gauge in the cockpit shows 2 bar while the actual pressure is 0.0 when i rev the engine.
I'm not sure what to do, i feel i have pretty much ruled out everything else. I'm afraid i may have missed something. If anyone has any suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal sent from the RPM sensor. The GM-style transmitter is similar to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily locate the spare in a salvage shop or a parts store. Test them out - put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black connector's end). They must be infinite ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that has to know the speed and position of the crankshaft in order to make decisions regarding timing of the fuel injector, for example. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these sensors, the diagnostic scanner will show the codes that could trigger the engine shutting down.
Some of the symptoms of a malfunctioning G28 sensor include an inaccurate gearbox rev counter the gears are shifting faster than normal and/or misfiring when in gear. It is likely that your sensor is failing and needs to be replaced if you experience any of these signs. They are cheap and easy-to-find particularly if they're an Bosch sensor like ours. If you prefer, GM's version of this part is an option.
5. Tachometer
A failing engine speed sensor could be the cause of many problems in your car. It is an important part of the transmission of your Audi, as it transmits information to the ECU about how fast or slowly the car's engine is spinning. When this sensor fails, it will disrupt the performance of the transmission and the other car's components.
The G5 engine speed sensor is located on the outside of the transmission, above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 through a grey wire. The ECU utilizes this signal to regulate fuel and boost, and also timig. It also relays it to the G5 Tachometer in instrument cluster. You can test for sensor failure by examining the continuity of the sensor to the tachometer. Also, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 and pin T26a/12. how to get a new audi key should show approximately 1000 ohms resistance between those points. This is a standard part 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 could be available in wrecking yards.