Why Nobody Cares About Audi G28
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 situated near the transmission's edge just above the flywheel gear. It transmits a signal the ECU via a grey wire (T55/49), then to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the outside of the transmission, above the flywheel ring. The sensor transmits an electrical signal through the grey wire to pin T55/49. The ECU utilizes this information to control fuel and boost. It also sends a signal to the G5 Tachometer located in the instrument cluster.
The sensor is used to connect the G40 Camshaft position Sensor. The ecu must know when the crankshaft reached TDC and also the position of the camshaft, so that it can activate the spark and injectors.
If this sensor fails to function, the ECU will display a P00160 error message. This means that the Crank Shaft is not in sync with the Intake Camshaft. It could also be a sign of a chain stretch or a jumpy chain link in the upper chain of timing. The code won't show without the additional information supplied by other sensors (G4 or G40).
Testing is a bit challenging because there are two pins for the connector and they perform different functions however the best method to test it is to measure resistance between the sensor and the ECU. When the sensor is fully functional, it should read around 1000 ohms. If you're experiencing issues with this sensor, look for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at a high speed I noticed a significant decrease in power. It was as if the engine had run out of gas. Or, my injectors weren't firing. I took out the spark plugs this morning and found that 3 were soaked with gasoline and the fourth was unclean. When I crank the engine without sparks, i place a tissue on the top of each hole in the injector, the 3 drenched with gazoline pop out, but the 4th stays shut. I tested the ground connection of ECU pins 14,30 and 48/55. I got zero ohm. So i assume the problem is in another place.
I also tried to reset the PID with no success. The car is able to start when the G28 is not plugged in and is running fine when it is plugged in but it still is experiencing intermittent misfires at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature of -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is zero.
I don't know what to do. I believe that I've ruled everything else out. But i am afraid I may have missed something. If anyone has any ideas please chime in! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal from the RPM sensor. The GM-style sender is identical to 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 salvage yard or at a parts store. Test them out - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector end up) and 2 (2nd from the left on the black connector's side). audi keys replacement must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines requires to be aware of the speed and position of the crankshaft to determine timing of fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you encounter a problem with either of these, the diagnostic scanner will show the codes that could trigger an engine shut down.
Some of the symptoms of a malfunctioning G28 sensor are an inaccurate rev counter for the gearbox the gears are shifting faster than normal and/or misfiring when in gear. If you experience any of these issues it is likely that your sensor is deteriorating and needs replacing. The good thing is that they are quite affordable and readily available particularly when you're looking at an Bosch model, like ours. Alternately, GM's version this part would be an option.
5. Tachometer
A faulty engine speed sensor could be a cause for numerous issues with your vehicle. It's a crucial component of the transmission of your Audi because it relays information to the ECU on how fast or slow the car's engine is turning. If this sensor fails, it could affect the performance of the transmission, as well as the other car's components.
The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It transmits signals via a gray wire to the ECU pin T55/49. The ECU then processes this signal to regulate fuel, timig and boost, and also sends it on to the G5 Tachometer located in the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see around 1000 ohms of resistance between these two 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 You may also find them in wrecking yards.