How to Replace an Audi G28 Engine Speed Sensor
In this video, Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. This 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 situated on the edge of transmission, directly above the flywheel ring. The sensor transmits an electrical signal through the grey wire to pin T55/49. The ECU uses this information to control boost and fuel. It also sends an indication to the G5 Tachometer located in 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 has reached TDC, and where the camshaft lies in order to activate the spark and injectors.
If this sensor fails the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync and could indicate the chain is stretched or a jump link on the upper chain of timing. The code won't appear without the additional information provided by other sensors (G4 or G40).
It can be a bit difficult to test since there are several pins on the connector, and each has its own functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. If the sensor is operational, it should be reading approximately 1000 ohms. If you're experiencing issues with this component, look for evidence of oil or coolant in the connector bay.
2. Injectors
Yesterday, while accelerating at full speed from the highway paytoll, i experienced a big cut in power like the engine is running out of gas or injectors are not firing at all. In the morning, i removed the spark plugs, 3 were drenched in gazoline, the 4th one was dry. When I crank the engine without sparks, i place a tissue on top of each injector hole and the 3 that were drenched in gazoline pop out, but the 4th stay shut. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 I get 0ohm. Therefore, i think the issue is elsewhere.
I also tried to reset the PID but without success. The car can start when the G28 is not plugged in and it runs perfectly when it is plugged in but it still has the intermittent misfire issue at higher RPM. The coolant temperature sensor (G62) shows the wrong temp value that is -49c even after unplugging it. Also i noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.
I'm not sure what to do, i think i've pretty much completely ruled out all other possibilities. I'm worried that i might have missed something. If anyone has suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal by the RPM sensor. The GM-style sender 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 from a parts store. audi a4 key replacement is simple to test them by putting your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's side). They should be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that has to know the position and speed of the crankshaft in order to make decisions regarding fuel injector timing etc. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go wrong, you will receive codes on the diagnostic scanner that could cause engine shut down.
A failing G28 sensor could cause an inaccurate gearbox speed counter, a gearbox that shifts more quickly than normal, or a misfire in the gear. If you are experiencing any of these problems, it is likely that your sensor is failing and should be replaced. They're inexpensive and easy to locate especially if they're an Bosch model like ours. Alternatively, GM's version of this component is an excellent choice.
5. Tachometer
A faulty engine speed sensor could be the reason behind many issues in your vehicle. It's a crucial component of the transmission of your Audi since it sends information to the ECU on how fast or slowly the engine is spinning. This sensor could cause the transmission to fail and other components in the car to be affected.
The G5 engine sensor is located near the edge of transmission, above the flywheel ring. It sends an electrical signal through a gray wire to the ECU pin T55/49. The ECU then processes the signal to control fuel, timig, and boost, and also transmitting it to the G5 tachometer in the instrument cluster. You can test for sensor failure by examining the continuity from the sensor to the tachometer. You can also check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 and pin T26a/12. It should show approximately 1000 ohms resistance between these two points. This part is common across the Audi 80-100-200-RS2 range, beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 Du You may also find some good ones in wrecking yards.