How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is located at the top of the transmission, above the flywheel ring gear. It transmits a signal to the ECU via the grey wire (T55/49) and then to the tachometer located 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 an uncolored wire. The ECU utilizes this information to regulate the amount of fuel and boost. 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 has to know when the crankshaft reached TDC, and the location of the camshaft so that it can activate the spark and injectors.
If this sensor fails, the ECU will throw a P00160 code which means the Crank Shaft and Intake Camshaft are not in sync and could indicate chain stretch or a jumped link on the upper timing chain. The code will not appear without the additional information provided by other sensors (G4 or G40).
It is a little tricky to test because there are different pins on the connector and each has its own functions. The best way to do it is to measure the resistance between the ECU and the sensor. If the sensor is functional, it should read approximately 1000 ohms. Look for signs of coolant, or oil in the connector bay if you have issues with this component.
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 aren't firing anymore. I pulled out the spark plugs this morning, three were soaked with gasoline and the 4th was dry. When I start the engine with no sparks, i place a tissue on the top of each hole in the injector and the 3 drenched with gazoline leap out, however the 4th one stays closed. I checked the ground connection of ECU pins 14,30 and 48/55. I found 0ohm. I think the issue is elsewhere.
I also tried to reset PID but without success. The car will start when the G28 is disconnected, but it works fine when the G28 plugged in. However, the intermittent misfire problem persists at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value -49c, even if I unplug it. I also noticed that the oil pressure gauge in the cockpit is showing 2 bar when the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do, as i believe that i've ruled out everything else. But i am afraid i might have missed something. Let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal sent 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. You can easily locate an extra in a wrecking shop or a parts store. It is simple to test them - simply put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They should 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 a decision about fuel injector timing etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these sensors go bad you will get codes on the diagnostic scanner which can lead to engine shutdown.
A failing G28 sensor can cause an inaccurate speed counter for your gearbox, a gearbox that shifts more quickly than normal, or an unfire when in gear. It is likely that your sensor is failing and requires to be replaced if you encounter any of these signs. They are cheap and easy-to-find especially if they're a Bosch sensor like ours. Alternatively, the GM version of this unit is also a good option.
5. Tachometer
A malfunctioning engine speed sensor could be a cause for a slew of issues in your vehicle. It is a crucial part of the Audi's transmission because it communicates to the ECU about how the car's crankshaft is rotating. This sensor can cause the transmission to fail and other components in the car to be affected.
The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It sends signals via gray wire to ECU pin T55/49. The ECU is then able to process this signal to control the flow of fuel, timig and boost as well as sends it on to the G5 tachometer inside the instrument cluster. audi key replacement can check for sensor failure by examining the continuity from 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 see an average resistance of 1000 ohms between these points. This part is common across the Audi 80-100-200-RS2 model, ranging from the 1985 MC all the way up to the 1997 UrS AN and 1995 RS2 DU You may also find good ones in wrecking yards.