How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. The sensor is situated near the edges of the transmission above the flywheel ring gear. It transmits a signal to the ECU via the grey wire (T55/49), then to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated at the edges of the transmission, just above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU utilizes this information to control boost and fuel. It also sends a signal to the G5 Tachometer located in the instrument cluster.
The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is located so that it can activate spark and injectors in the right way.
If this sensor fails the ECU will display a P00160 code which means the Crank Shaft and Intake Camshaft are not in sync and possibly indicating the chain is stretched or a jump link on the upper timing chain. The code will not appear without the additional information provided by other sensors (G4 or G40).
It can be a bit difficult to test because 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. It should read around 1000 ohms when the sensor is operating at its maximum. Examine for evidence of coolant or oil in the connector bay if you have issues with this part.
2. Injectors
Yesterday, when i was accelerating to the fullest speed from highway paytoll, i experienced a big cut in power like the engine is running out of gas or the injectors are not firing at all. Today, i pulled out the spark plugs, 3 were soaked with gazoline and the 4th one was dry. I put a piece of tissue over each injector hole and when I start the engine with no sparks, the three with gazoline jump out. The 4th one remains closed. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found zero ohm. I'm assuming that the issue is in another location.
I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However the intermittent misfire issue still occurs at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is 0.
I'm not sure what to do. I think 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 in the g28 can be activated by a signal sent by the RPM sensor. The GM-style transmitter is identical 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. It is simple to test them - put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's side). They should be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines must know the position and speed the crankshaft to make decisions regarding timing of fuel injectors, 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 show the codes that could trigger an engine shut down.
Some of the signs of a failing G28 sensor are an inaccurate rev counter for the gearbox and gears that shift faster than normal and/or a misfire when in gear. If you have any of these issues, it is likely your sensor is failing and requires replacement. The good news is that they are very affordable and easily accessible particularly when you're looking at a Bosch sensor, which is what ours are. Alternatively, GM's version of this component is an option.
5. Tachometer
A malfunctioning engine speed sensor could be the reason behind many issues in your car. It's a vital component of your Audi's transmission, because it communicates to the ECU about how the car's crankshaft is spinning. This sensor could cause the transmission to fail and other components in the car to be affected.
audi replacement key is located at the outside of the transmission, above the flywheel ring gear. It sends a signal to the ECU at pin T55/49 through an uncolored wire. The ECU utilizes this signal to regulate the amount of fuel and boost, and also to timigrate. It also transmits it to the G5 Tachometer in instrument cluster. You can determine if the sensor is in failure by examining the continuity from the sensor to the tachometer. You can also verify continuity between pin 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. You should see approximately 1000 ohms of resistance between these two points. This is a standard part that is found 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.