How to Replace an Audi G28 Engine Speed Sensor
In this video, Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. This sensor is located at the top of the transmission, above the flywheel ring gear. It sends a signal to the ECU via a grey wire (T55/49), 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 an electrical signal to ECU pin T55/49 via a grey wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends an alert to the G5 Tachometer within the instrument cluster.
The sensor is used to connect with the G40 Camshaft position Sensor. The ecu has to know when the crankshaft has reached TDC, and the location of the camshaft 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 an issue with the chain or a jump in the chain link of the upper timing chain. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).
Testing is a bit challenging because there are two pins for the connector and they have different functions however the best way to test it is to measure resistance between the sensor and the ECU. When the sensor is functional, it should read about 1000 ohms. Look for signs of coolant or oil in the connector bay if you are experiencing issues with this part.
2. Injectors
Yesterday, while accelerating at full speed from the highway paytoll i had an abrupt drop in power like the engine is running out of gas or injectors are not firing anymore. I took out the spark plugs this morning, 3 were soaked in gasoline, and the fourth was unclean. When I crank the engine without sparks, I put a piece of tissue on the top of each hole in the injector and the 3 drenched with gazoline leap out, however the 4th stays shut. I checked the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. So i assume the problem is elsewhere.
I also tried to reset the PID with no how much is a replacement audi key success. The car is able to start when the G28 is disconnected and it runs perfectly when it is connected but it still has the intermittent misfire issue at higher RPM. The coolant sensor (G62), even when unplugged, still shows a temperature of -49c. I also noticed that the oil pressure gauge in the cockpit shows 2 bar while the actual pressure is 0.0 if i crank up the engine.
I'm not certain what to do, click here as i feel i have pretty much ruled out everything else. I'm afraid i may have missed something. Please let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter is identical to the G4 and both function in the more info 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 - just switch your DMM into new audi car key resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines have an ECU that needs to be aware of the speed and position of the crankshaft in order to make decisions regarding timing of the fuel injector, for example. To do this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either one of these, the diagnostic scanner will display codes that could lead to an engine shutdown.
A malfunctioning G28 sensor can cause an inaccurate speed counter for your gearbox or a gearbox that shifts more quickly than normal, and/or an unfire when in the gear. It is likely that the sensor is failing and requires to be replaced if you experience any of these symptoms. The good thing is that they are very cheap and easily accessible particularly in the case of an Bosch unit which is what we have. Alternately, the GM version of this unit is also a great option.
5. Tachometer
A malfunctioning engine speed sensor could be the reason behind numerous issues with your car. It is an important part of the transmission in your Audi since it sends information to the ECU regarding how fast or slow the engine of the car is spinning. 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, over the flywheel ring. It sends signals via an uncolored wire to the ECU pin T55/49. The ECU then uses and processes this signal to regulate fuel, timig and boost as well as transmitting it to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. You can also examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]), get more info and between pin T6a/1 and pin T26a/12. You should observe approximately 1000 ohms resistance between these two points. This is a common part that is found across the Audi 80 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best ones could be available in wrecking yards.