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. The sensor is located on the edge of the transmission above the flywheel ring gear. It sends a signal to the ECU via an uncolored wire (T55/49) which is then sent to the tachometer within the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the edge of transmission, above the flywheel ring. This sensor sends signals through the grey wire to pin T55/49. The ECU utilizes this information to control the amount of fuel and boost. how much is a replacement audi key sends a signal to the G5 tachometer inside the instrument cluster.
The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft reached TDC and also where the camshaft lies to trigger the spark and injectors.
If this sensor fails to function, the ECU will display an error code P00160. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumped chain link in the upper chain. However the code will not appear on its own without additional information from other sensors (G4 and G40).
Testing is a bit challenging because there are two connector pins, and they perform different functions but the best method to test it is to measure resistance between the sensor and the ECU. It should read approximately 1000 ohms if the sensor is at full operation. Check for evidence of coolant or oil in the connector bay if there are issues with this component.
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 out of gas or injectors are not firing any more. I pulled out the spark plugs this morning and found that 3 were soaked in gasoline, and the fourth was unclean. I placed a tissue over each injector hole, and when I turn the engine on without sparks, the three with gazoline jump out. The 4th one remains shut. I tested the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I get zero ohm. I assume that the problem is somewhere else.
I also tried to reset the PID but with no luck. The car can start if the G28 is disconnected and runs fine when it is plugged in but it still is experiencing intermittent misfires 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 when the actual pressure is zero.
I'm not sure what to do. I feel like i've pretty much all other possibilities out. I'm concerned that i may have missed something. Please let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style transmitter is the same as the G4 and they both work in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or in a local parts store. It is simple to test them by putting your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's side). They must 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 decisions about timing of the fuel injectors, etc. To do this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these sensors, the diagnostic scanner will display the codes that could trigger an engine shutdown.
A damaged G28 sensor could result in an inaccurate speed counter for the gearbox, a gearbox that shifts more quickly than normal, or a misfire in the gear. It is likely that your sensor is failing and needs to be replaced if you notice any of these symptoms. The good news is they are quite affordable and easily accessible, especially if you're looking at a Bosch sensor, which is what ours are. Alternately, GM's version this component is an excellent choice.
5. Tachometer
A failing engine sensor could cause a number of problems within your vehicle. It is an important part of the transmission of your Audi since it sends information to the ECU on how fast or slow the engine is turning. This sensor could cause the transmission to malfunction and other components in the car to be affected.
The G5 engine speed sensor is situated on the outside of the transmission above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49, via an uncolored wire. The ECU then uses and processes this signal to regulate fuel, timig, and boost and then sends it on 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]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should see an average resistance of 1000 ohms between these two points. This is a typical 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. Good ones could be available in wrecking yards.