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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 located at the edge of transmission over the flywheel gear. It transmits a signal the ECU via an uncolored wire (T55/49), then to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 using a grey wire. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends an indication to the G5 tachometer in the instrument cluster.
The sensor is used to connect the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is located so that it can trigger spark and injectors in the right way.
If this sensor fails to function, the ECU will display an error code P00160. This indicates that the Crank Shaft is out of line with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumpy chain link in the upper timing chain. The code won’t appear without the additional information provided by other sensors (G4 or G40).
It can be a bit difficult to test as there are different pins on the connector, and they all have different functions. The best way to do it is to measure the resistance between the ECU and the sensor. If the sensor is operational, it should be reading approximately 1000 ohms. If you’re having issues with this sensor, look for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday accelerating full speed from highway paytoll, I experienced a big cut in power like the engine is out of gas or the injectors aren’t firing any more. I pulled out the spark plugs this morning and found that 3 were soaked with gasoline and the fourth was dry. I placed a tissue over each hole in the injector and when I start the engine with no sparks, the ones that have gazoline pop right out. The fourth one remains shut. I tested the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. I’m assuming that the issue is in another location.
I also tried to reset PID without success. The car can start when the G28 is not plugged in and is running fine when it is plugged in but it still is experiencing intermittent misfires at higher RPM. The coolant sensor (G62), even when it is unplugged, shows a temperature of -49c. Also, i noticed that the gauge for oil pressure 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 think i’ve pretty much completely ruled out all other possibilities. But i am afraid I may have missed something. Let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal by the RPM sensor. The GM-style transmitter functions similarly to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. It is easy to find the spare in a salvage shop or parts store. It is simple to test them – just switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector’s end facing up). replacement audi key should be infinite ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to know the position and speed the crankshaft in order to make a decision about 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 have a problem with either of these, the diagnostic scanner will display the codes that could trigger an engine shut down.
Some of the signs of a malfunctioning G28 sensor include an inaccurate gearbox rev counter and gears that shift faster than normal and/or a misfire when in gear. It is probable that the sensor is failing and needs to be replaced if you encounter any of these symptoms. They’re cheap and easy to find, especially when they’re a Bosch unit like ours. Alternately, GM’s version this part is a good option.
5. Tachometer
A failing engine speed sensor could be the cause of numerous problems in your vehicle. It is a crucial part of the Audi’s transmission as it sends information to the ECU about how fast or slow the vehicle’s crankshaft is spinning. When this sensor fails, it could cause problems for the transmission, as well as the rest of the car’s components.
The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It sends a signal via an uncolored wire to the ECU pin T55/49. The ECU utilizes this signal to control the flow of fuel and boost as well as timig. It also sends it to the G5 Tachometer located in the instrument cluster. You can check for sensor failure by examining the continuity from the sensor to the tachometer. Also, you can 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 detect a resistance of approximately 1000 ohms between these points. This part is common across the Audi 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS An and 1995 RS2 Du You may also find good ones in wrecking yards.