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 on the edge of the transmission above the flywheel ring gear. It sends a signal to the ECU via the grey wire (T55/49) and then to the tachometer within 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 signals to ECU pin T55/49 using an uncolored wire. 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.
audi a3 key replacement is used to link with the G40 Camshaft position Sensor. The ecu must know when the crankshaft has reached TDC and also the position of the camshaft, to trigger the spark and injectors.
If this sensor fails to function, the ECU will display an error code P00160. This means that the Crank Shaft is not in sync with the Intake Camshaft. It could also indicate a chain stretch or a jumped chain link in the upper timing chain. The code will not appear without the additional information provided by other sensors (G4 or G40).
It's a bit tricky to test as there are several connector pins, and each one has different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. It should read about 1000 ohms when it is at full operation. Look for signs of coolant or oil in the connector bay if there are issues with this component.
2. Injectors
Yesterday accelerating full speed from highway paytoll i had massive power loss like the engine is running out of gas or injectors aren't firing at all. I took out the spark plugs this morning, 3 were soaked with gasoline and the fourth was unclean. I put a piece of tissue over each injector hole, and when i start the engine without sparks, the ones with gazoline jump right out. The 4th one stays shut. I tested the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. So i assume the problem is in another place.
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 still occurs 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 gauge for oil pressure in the cockpit is showing 2 bar while the actual pressure is 0.0 when i rev the engine.
I'm not sure what to do, but i feel i have pretty much ruled out everything else. However, i'm afraid that i might have missed something. If anyone has any suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal by the RPM sensor. The GM-style sensor is identical to the G4 and both function in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or in a local parts store. It is easy to test them - simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector's end facing up). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines needs to know the speed and position of the crankshaft in order to make a decision about fuel injector timing, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you encounter a problem with either of these, the diagnostic scanner will display codes that could lead to an engine shut down.
Some of the symptoms of a failed G28 sensor are an inaccurate gearbox rev counter the gears are shifting faster than normal and/or misfiring when in gear. If you are experiencing any of these issues, it is most likely that your sensor is failing and needs replacing. They are cheap and easy-to-find especially if they're a Bosch unit like ours. You can also choose the GM version of this component is also a good choice.
5. Tachometer
A failing engine speed sensor could be the reason behind numerous issues with your vehicle. It's an essential component of your Audi's transmission, as it sends information to the ECU about how the car's crankshaft is spinning. If this sensor fails, it will affect the performance of the transmission as well as the other car's components.
The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It transmits an electrical signal through gray wire to ECU pin T55/49. The ECU is then able to process this signal to regulate fuel, timig and boost, and also sends it on to the G5 tachometer inside 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]) and between T6a/1 and the instrument cluster pin T26a/12. You should see around 1000 ohms of resistance between those two pins. This is a common feature across the Audi 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 Du So, you may find them in wrecking yards.