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 at the edge of transmission, above the flywheel gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located at the edges of the transmission, above the flywheel ring. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then uses this information to control the boost, fuel, and timig. It also sends signals to the G5 tachometer in the instrument cluster.
The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft has reached TDC, and the position of the camshaft, in order to activate the spark and injectors.
If this sensor fails to function, the ECU will display a P00160 error code. This indicates 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 jump in the chain link of the upper timing chain. However, the error code won't be displayed on its own without additional information from other sensors (G4 and G40).
Testing can be a bit difficult because there are two pins for the connector and they perform different functions but the best way to test it is to measure the resistance between the sensor and the ECU. When the sensor is operational, it should be reading approximately 1000 ohms. Look for signs of coolant, or oil in the connector bay if you are experiencing problems with this part.
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 running out of gas or the injectors are not firing any more. Today, i pulled out the spark plugs. Three were drenched with gazoline the fourth one was dry. When i crank the engine, there are no sparks i put tissue on top of each injector hole, the 3 drenched with gazoline leap out, however the 4th stay shut. I tried to test the ground connections of ECU pins 14,30, and 48/55. I found zero ohm. I assume that the problem is somewhere else.
I also tried to reset the PID without success. The car will start when the G28 is disconnected, but it is running fine with the G28 connected. However, audi a1 key 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 bars but the actual pressure is zero.
I'm not sure what to do, i feel i have pretty much completely ruled out all other possibilities. But i am afraid i might have missed something. If anyone has suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals from the RPM sensor. audi a1 key -style transmitter is the same as the G4 and both function in the 80 100 200, UrS and RS2 cars so you can easily find one at a junkyard or in a local parts store. It is simple to test them: simply put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They should be infinite Ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that must be aware of the speed and position of the crankshaft in order to make a decision about timing of the fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you are experiencing issues with either of these, the diagnostic scanner will show codes that could lead to an engine shut down.
A malfunctioning G28 sensor can cause an inaccurate gearbox speed counter or a gearbox that shifts more quickly than normal, or an unfire when in gear. It is possible that the sensor is failing and requires to be replaced if you notice any of these signs. The good news is that they are quite affordable and easy to find, especially in the case of the Bosch unit which is what ours are. If you prefer, GM's version of this part is a good option.
5. Tachometer
A failing engine speed sensor could be a cause for a slew of issues in your car. 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. This sensor can cause the transmission to fail and other car components to be affected.
The G5 engine sensor is located near the edge of transmission, above the flywheel ring. It sends signals via an uncolored wire to the ECU pin T55/49. The ECU then processes this signal to control the flow of fuel, timig and boost and then transmitting 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 to pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see approximately 1000 ohms resistance between those points. This part is common across the Audi 80-100-200-RS2 series, starting 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.