How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. This sensor is located on the outside of the transmission over the flywheel gear. It sends a message to the ECU via the grey wire T55/49 and then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using an uncolored wire. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends an indicator to the G5 Tachometer within the instrument cluster.
The sensor is used to connect 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 display a P00160 error code. This indicates that the Crank Shaft is not in sync with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumpy chain link in the upper chain of timing. The code will not appear without the additional information supplied by other sensors (G4 or G40).
It's a bit tricky to test because there are several pins on the connector, and each one has 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 read about 1000 ohms. If you're experiencing issues with this sensor, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, when i was accelerating to the fullest speed from highway paytoll, I experienced massive power loss like the engine is running out of gas or the injectors are not firing anymore. This morning i pull out the spark plugs, 3 were drenched with gazoline the fourth one was dry. I put tissue over each injector hole and when I turn the engine on without sparks, the ones that have gazoline pop right out. The 4th one stays closed. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I got 0ohm. I think the issue is somewhere else.
I also tried to reset PID without success. The car is able to start when the G28 is disconnected and is running fine when it is connected, but still has the intermittent misfire issue at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature of -49c, even if I unplug it. Also, i 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. I believe that I've all other possibilities out. I'm afraid i may have missed something. Please let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal sent from the RPM sensor. The GM-style sender is identical to the G4 and both function in the 80 100 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or at a 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 on the connector's edge facing up). They should be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that must know the speed and position of the crankshaft in order to make a decision about fuel injector timing etc. To accomplish this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either of these, the diagnostic scanner will show the codes that could trigger the engine shutting down.
A damaged G28 sensor can cause an inaccurate gearbox speed counter and a gearbox which shifts more quickly than normal, and/or a misfire in gear. If you experience any of these issues, it is likely that your sensor is going bad and should be replaced. The good news is they are very cheap and easily accessible particularly if you're looking at a Bosch model, which is what ours are. Alternately, audi key replacement near me of this unit is also a good option.
5. Tachometer
A damaged engine sensor could cause a variety of issues in your vehicle. It's a crucial component of the transmission in your Audi since it sends information to the ECU on how fast or slow the engine of the car is spinning. If this sensor fails, it can cause problems for the transmission as well as the other car's components.
The G5 engine speed sensor is located on 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 control the amount of fuel and boost, and also to timigrate. It also sends it to the G5 Tachometer inside the instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see an average resistance of 1000 ohms in these areas. This part is common across the Audi 80-100-200-RS2 range, from the 1985 MC all the way up to the 1997 UrS An and 1995 RS2 Du, so you might find some good ones in wrecking yards.