How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. The sensor is situated at the top of the transmission, above the flywheel ring gear. It transmits a signal to the ECU via a grey wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated at the edges of the transmission, above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU then uses this information to control the boost, fuel, and timig. It also sends a signal 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 must know when the crankshaft is TDC and where the camshaft is located so that it can start spark and injectors according to the situation.
If this sensor fails, the ECU will display a P00160 error message. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumpy chain link in the upper timing chain. However the code will not appear on its own, without additional information from other sensors (G4 and G40).
Testing is a bit challenging as there are two different connector pins and they serve different purposes but the best method to test it is to measure the resistance between the sensor and the ECU. advice here should read approximately 1000 ohms when the sensor is in full operation. Examine for signs of coolant, or oil in the connector bay if you are experiencing problems with this part.
2. Injectors
Yesterday, while accelerating at full speed from the highway paytoll i had a big cut in power like the engine is out of gas or the injectors are not firing any more. In the morning, i removed the spark plugs. Three were drenched with gazoline the fourth was dry. audi a4 car key replacement placed a tissue over each injector hole, and when i start the engine without sparks, the three that have gazoline pop right out. The 4th one stays shut. I tested the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. I think the issue is elsewhere.
I also tried to reset the PID without success. The car can start if the G28 is unplugged and is running fine when it is plugged in however it is experiencing intermittent misfires at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0.
advice here 'm not sure what to do, i feel i have pretty much ruled out everything else. But i am afraid i might have missed something. If anyone has any suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal from the RPM sensor. The GM-style transmitter is identical to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or parts store. Testing them is easy 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 end of the connector). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines requires to know both the position and speed the crankshaft to make decisions regarding fuel injector timing, etc. To accomplish this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either one of these, the diagnostic scanner will display codes that could cause the engine shutting down.
A damaged G28 sensor could cause an inaccurate gearbox speed counter or a gearbox that shifts more quickly than normal, and/or an unfire when in the gear. It is probable that the sensor is failing and requires to be replaced if you experience any of these signs. The good news is they are very cheap and readily available, especially if you're looking at a Bosch sensor, which is what we have. Alternately, GM's version this part would be an option.
5. Tachometer
A failing engine sensor could cause a myriad of issues in your car. It's a crucial component of the transmission of your Audi, as it transmits information to the ECU regarding 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 speed sensor is located at the outside of the transmission just above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49, via an uncolored wire. The ECU then processes this signal to regulate fuel, timig, and boost, and also sends it on to the G5 tachometer in the instrument cluster. You can check the sensor for failure by examining the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should detect an average resistance of 1000 ohms between these two points. This is a common component across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.