How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. read here is located near the edges of the transmission just above the flywheel ring gear. It sends a message to the ECU via the grey wire T55/49 and then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via an uncolored wire. The ECU uses this information to control the amount of fuel and boost. It also sends an alert to the G5 Tachometer within the instrument cluster.
The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft reached TDC and also the location of the camshaft in order to activate the spark and injectors.
If this sensor fails, the ECU will display an error code P00160. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also be a sign of an issue with the chain or a jump in the chain link of the upper timing chain. However the code will not appear on its own, without additional information from other sensors (G4 and G40).
Testing is a bit tricky since there are two pins for the connector and they have different functions however the best method to test it is to measure the resistance between the sensor and the ECU. When the sensor is fully operational, it should be reading approximately 1000 ohms. If you're experiencing issues with this component, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, while accelerating from the highway paytoll at maximum speed I noticed a significant decrease in power. It was like the engine had run out of gas. Or my injectors were not firing. This morning i pull out the spark plugs. Three were soaked with gazoline and the fourth one was dry. When I start the engine without sparks i put tissue on the top of each hole in the injector and the 3 that were drenched in gazoline jump out but the 4th stays closed. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I get 0ohm. I'm assuming that the issue is in another location.
I also tried to reset PID but without success. The car will start when the G28 is disconnected, but it runs fine with the G28 connected. However, the intermittent misfire problem continues to occur 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 but the actual pressure is zero.
I'm not sure what to do. I believe that I've ruled everything else out. But i am afraid I might have missed something. If anyone has any suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style sender is the same as the G4 and both are used in the 80 100, 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or from a parts store. It is simple to test them - simply switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump on the connector's edge facing up). 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 to make a decision about fuel injector timing etc. To do this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go bad you will get codes on the diagnostic scanner that can cause the engine to shut down.
A malfunctioning G28 sensor could cause an inaccurate gearbox speed counter, a gearbox that shifts faster than normal, and/or a misfire 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 particularly in the case of a Bosch unit like ours. Alternatively, the GM version of this component is also a good choice.
5. Tachometer
A malfunctioning engine sensor can cause a myriad of issues in your vehicle. It's an essential component of the Audi's transmission because it communicates to the ECU about how fast or slow the car's crankshaft is spinning. If the sensor fails, it will disrupt the performance of the transmission and the other car's components.
The G5 engine speed sensor is situated on the edge of the transmission above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 through a grey wire. The ECU then processes this signal to regulate the flow of fuel, timig and boost and then sends it on to the G5 Tachometer located in the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see a resistance of approximately 1000 ohms between these points. This is a typical 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. Good ones might be availble in wrecking yards.