How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows 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 an uncolored wire T55/49, then to the tachometer on the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated on the outside of the transmission, just above the flywheel ring. The sensor transmits an electrical signal through the grey wire to pin T55/49. The ECU utilizes this information to regulate boost and fuel. 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 has to know when the crankshaft reached TDC, and the position of the camshaft, to trigger the spark and injectors.
If this sensor fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is not in sync with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumpy chain link in the upper timing chain. The code won't show without the additional information provided by other sensors (G4 or G40).
Testing can be a bit difficult because there are two connector pins, and they serve different purposes however the best method to test it is to measure the resistance between the sensor and the ECU. It should read about 1000 ohms when the sensor is in full operation. Examine for evidence of coolant or oil in the connector bay if you have 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 running out of gas or the injectors are not firing anymore. This morning i pull out the spark plugs, 3 were drenched in gazoline, the 4th one was dry. When I start the engine with no sparks, i place a tissue on top of each injector hole and the 3 drenched with gazoline leap out, however the 4th stay closed. I tried to test the ground connections of ECU pins 14,30, and 48/55. I found 0ohm. Therefore, i think the issue is in another place.
I also tried to reset the PID but without success. The car is able to start when the G28 is disconnected and it runs perfectly when it is connected however it has intermittent misfire issues at higher RPM. The coolant sensor (G62), even when unplugged, still website shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is zero.
I'm not certain what to do, but i think i've pretty much completely ruled out all other possibilities. But i am afraid i might have missed something. If anyone has suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal sent read more by 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 wrecking yard or at a parts store. It is simple to test them - just put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines requires to know the speed and position of the crankshaft to determine timing of fuel injectors, etc. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these, the diagnostic scanner will display codes that could lead to the engine shutting down.
Some of the signs of a failed G28 sensor are an inaccurate gearbox rev counter the gears are shifting faster than normal, and/or a misfire when you are in gear. If you are experiencing any of these issues it is most likely that your sensor is failing and requires replacement. The good news is that they are very affordable and readily available, especially if you're looking at the Bosch unit which is what ours are. Alternatively, GM's version of this part is an option.
5. Tachometer
A failing engine sensor could cause a myriad of issues in your vehicle. It's an essential component of the transmission of your Audi, as it transmits information to the ECU on how fast or slowly the engine of the car is spinning. If this sensor fails, it could disrupt the performance of the transmission and the rest of the car's components.
The G5 engine speed sensor is situated on the edge of the transmission just above the flywheel ring gear and sends a signal to the ECU at pin T55/49 via click here a grey wire. The ECU uses this signal to control the amount of fuel and boost, and also to timigrate. It also relays it to the G5 Tachometer inside the instrument cluster. You can determine if the sensor is in failure by examining the continuity from the sensor to the tachometer. You can also examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 as well as pin T26a/12. You should observe around 1000 ohms of more info resistance between those points. This is a typical part that is found across the Audi 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU get more info so good ones might be availble in wrecking yards.