7 Small Changes You Can Make That'll Make The Biggest Difference In Your 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 at the edge of transmission, above the flywheel gear. It transmits a signal to the ECU through a grey wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The sensor is located at the edge of the transmission above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through an uncolored wire. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an alert to the G5 Tachometer located in the instrument cluster.
The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is located so that it can activate spark and injectors according to the situation.
If this sensor fails when it fails, 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 jumped chain link in the upper chain of timing. The code won't show without the additional information supplied by other sensors (G4 or G40).
It can be a bit difficult to test as there are several pins on the connector, and each one has different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. When the sensor is fully functional, it should read around 1000 ohms. Look for evidence of coolant or oil in the connector bay if you have issues with this component.
2. Injectors
Yesterday, when accelerating from highway paytoll at maximum speed, i noticed a huge decrease in power. It was as if the engine was running out of gas. Or, my injectors were not firing. I pulled out the spark plugs this morning and found that 3 were drenched in gasoline and the 4th was dry. I placed a tissue over each hole in the injector and when i start the engine with no sparks, the three with gazoline jump right out. The 4th one remains shut. I tested the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. I'm assuming that the issue is in another location.
I also tried to reset the PID without success. The car will start when the G28 is not plugged in and runs fine when it is plugged in but it still is experiencing intermittent misfires at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows an ice temperature of -49c. I also noticed that the oil pressure gauge in the cockpit is showing 2 bar when the actual pressure is 0.0 when i rev the engine.
I'm not sure what to do, i feel i have pretty much completely ruled out all other possibilities. However, i'm afraid that I might have missed something. If anyone has suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style sender 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 wrecking yard or from a parts store. It is easy 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 must be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that needs to know the speed and position of the crankshaft to make decisions regarding timing of the fuel injectors, etc. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go bad you will get codes on the diagnostic scanner that can lead to engine shutdown.
A failing G28 sensor can cause an inaccurate speed counter for your gearbox or a gearbox that shifts faster than normal, and/or a misfire while in the gear. It is likely that the sensor is failing and needs to be replaced if you encounter any of these signs. The good thing is that they are very cheap and easy to find particularly in the case of a Bosch sensor, which is what ours are. Alternatively, the GM version of this unit is also a good choice.
5. Tachometer
A failing engine sensor could cause a number of problems in your vehicle. It is an important part of the transmission in your Audi, as it transmits information to the ECU regarding how fast or slow the engine is spinning. When this sensor fails, it could cause problems for the transmission, as well as the other car's components.
The G5 engine speed sensor is located on the edge of the transmission above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 via a grey wire. The ECU then uses and processes this signal to control fuel, timig, and boost, and also transmitting it to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by examining the continuity of the sensor to the tachometer. You can also verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]) and between pin T6a/1 as well as pin T26a/12. advanced key audi should show approximately 1000 ohms of resistance between those points. This is the same across the Audi 80-100-200-RS2 model, ranging beginning with the 1985 MC and up to the 1997 UrS AN and the 1995 RS2 Du, so you might find good ones in wrecking yards.