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 transmits a signal to the ECU through an uncolored wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
The grey wire is located at the edges of the transmission, above the flywheel ring. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends an alert to the G5 Tachometer located in the instrument cluster.
The sensor serves as a reference for comparing 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 in the right way.
If this sensor fails when it fails, the ECU will display a P00160 error code. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jump in the chain link of the upper timing chain. However, the error code won't be displayed on its own without additional information from other sensors (G4 and G40).
It can be a bit difficult to test as there are different pins on the connector and each has its own functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. It should read approximately 1000 ohms if the sensor is operating at its maximum. Look for signs of coolant, or oil in the connector bay if there are issues with this part.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at a high speed, i noticed a huge reduction in power. It was like the engine had run out of gas. Or my injectors were not firing. lost audi keys pull out the spark plugs. Three were drenched with gazoline the fourth one was dry. When I crank the engine without sparks, I put a piece of tissue on the top of each hole in the injector, the 3 drenched with gazoline leap out, however the 4th stay shut. I tested the ground connection of ECU pins 14,30 and 48/55. I found zero ohm. I'm assuming that the issue is in another location.
I also tried to reset the PID but with no luck. The car is able to start if the G28 is unplugged and runs fine when it is connected but it still is experiencing intermittent misfires at higher RPM. The coolant sensor (G62), even when it is unplugged, shows an ice temperature of -49c. Also i noticed that the gauge for oil pressure in the cockpit shows 2 bar while the actual pressure is 0.0 when i rev the engine.
I don't know what to do. I believe that I've ruled everything else out. However, i'm afraid that I might have missed something. If anyone has any suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal by 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 junkyard or in a local parts store. It is simple to test them: simply switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector's end facing up). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that has to know the speed and position of the crankshaft to make a decision about fuel injector timing etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either of these sensors, the diagnostic scanner will display codes that could lead to an engine shut down.
Some of the signs of a malfunctioning G28 sensor include an inaccurate gearbox rev counter, gears shifting quicker than normal, and/or a misfire when you're in gear. It is probable that the sensor is failing and requires to be replaced if you encounter any of these symptoms. The good news is they are very cheap and readily available, especially in the case of a Bosch unit which is what ours are. Alternately, the GM version of this component is also a good choice.
5. Tachometer
A failing engine speed sensor could be the reason behind a slew of problems in your car. It is a crucial part of your Audi's transmission, because it communicates to the ECU about how the car's crankshaft is spinning. If the sensor fails, it could affect the performance of the transmission, as well as the rest of the car's components.
The G5 engine speed sensor is located at the edge of the transmission just above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49, via a grey wire. The ECU utilizes this signal to regulate fuel and boost, as well as timig. It also relays it to the G5 Tachometer located in the instrument cluster. You can test for sensor failure by examining the continuity from the sensor to the tachometer. Also, you can verify continuity between pin 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 see approximately 1000 ohms resistance between these two points. This is a common component across the Audi 80 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good ones could be available in wrecking yards.