How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located at the edge of transmission, above the flywheel gear. It transmits a signal to the ECU via an uncolored wire (T55/49) and then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 through the grey wire. The ECU utilizes this information to control boost and fuel. It also sends an alert to the G5 Tachometer in instrument cluster.
The sensor is used to correlate the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft reached TDC, and where the camshaft lies in order to activate the spark and injectors.
If this sensor fails to function, the ECU will display an error code P00160. This indicates that the Crank Shaft is not in alignment with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumpy chain link in the upper chain. The code will not appear without the additional information provided by other sensors (G4 or G40).
It is a little tricky to test since 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. When the sensor is fully operational, it should read around 1000 ohms. If you are having problems with this component, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at maximum speed I noticed a massive decrease in power. It was like the engine was running out of gas. Or, my injectors were not firing. In the morning, i removed the spark plugs, 3 were soaked with gazoline and the fourth was dry. I placed a tissue over each injector hole, and when I start the engine without sparks, the 3 with gazoline jump out. The 4th one remains closed. I checked the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. So i assume the problem is elsewhere.
I also tried to reset PID without success. The car can start when the G28 is not plugged in and runs fine when it is plugged in but it still is experiencing intermittent misfires at higher RPM. The coolant sensor (G62) even when unplugged, still shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is 0.
I'm not sure what to do, but i believe that i've ruled out everything else. I'm worried that i might have missed something. If anyone has suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals 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 an extra in a wrecking shop or parts store. Test them out by putting your DMM in resistance mode and measure between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black connector's end). They should be infinite ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that needs to know the position and speed of the crankshaft in order to make decisions about timing of the fuel injector, for example. In order to do this it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes wrong, you will receive codes on the diagnostic scanner that can cause the engine to shut down.
A damaged G28 sensor can cause an inaccurate speed counter for your gearbox, a gearbox that shifts more quickly than normal, or a misfire while in gear. If you experience any of these issues, it is likely your sensor is deteriorating and requires replacement. The good news is that they are very affordable and easy to find, especially in the case of an Bosch model, like ours. You can also choose the GM version of this unit is also a great option.
5. Tachometer
A malfunctioning engine sensor can cause a myriad of issues in your vehicle. It's an essential component of the transmission of your Audi, as it transmits information to the ECU about how fast or slow the engine of the car is spinning. If audi car key fails, it could affect the performance of the transmission as well as the rest of the car's components.
The G5 engine sensor is located at the outskirts of the transmission, over the flywheel ring. It transmits a signal via gray wire to ECU pin T55/49. The ECU then processes the signal to control fuel, timig and boost and then transmitting it to the G5 Tachometer located in the instrument cluster. You can check 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 as well as pin T26a/12. You should detect the resistance to be around 1000 ohms between these two points. 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 ones might be availble in wrecking yards.