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 located on the edge of the transmission just above the flywheel ring gear. It sends a signal to the ECU via an uncolored wire (T55/49) and then to the tachometer located in the instrument cluster.
1. had me going is situated on the outside of the transmission, directly above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU uses this information to regulate the amount of fuel and boost. It also sends signals to the G5 tachometer inside the instrument cluster.
The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft has reached TDC, and the location of the camshaft so that it can activate the spark and injectors.
If this sensor fails to function, the ECU will display an error code P00160. This means that the Crank Shaft is out of line 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. However, the code won't appear on its own, without additional information from other sensors (G4 and G40).
It is a little tricky to test as there are several pins on the connector and each one has different functions. The best way to do it is to measure the resistance between the ECU and the sensor. It should read around 1000 ohms if the sensor is at full operation. If replacement audi car key are having problems with this part, check for evidence of oil or coolant in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at a high speed, i noticed a huge drop in power. It was like the engine was running out of gas. Or, my injectors weren't firing. I pulled out the spark plugs this morning and found that 3 were soaked in gasoline, and the fourth was unclean. I put a piece of tissue over each injector hole and when i start the engine without sparks, the ones with gazoline jump out. The fourth one remains closed. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. i get zero ohm. I think the issue is elsewhere.
I also tried to reset the PID without success. The car will start if the G28 is unplugged and runs fine when it is connected however it has intermittent misfire issues at higher RPM. The coolant sensor (G62), even when unplugged, still shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is 0.
I'm not sure what to do, but i feel i have pretty much eliminated everything else. I'm concerned that i may have missed something. Please let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals from the RPM sensor. The GM-style sensor 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 to do - just put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's side). They must be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines must know the speed and position of the crankshaft to make decisions regarding timing of the fuel injector, etc. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these, the diagnostic scanner will display codes that could lead to the engine shutting down.
Some of the symptoms of a malfunctioning G28 sensor are an inaccurate rev counter in the gearbox and gears that shift faster than normal and/or a misfire when in gear. It is possible that the sensor is failing and needs to be replaced if you experience any of these symptoms. They're inexpensive and easy to locate, especially in the case of an Bosch unit like ours. If you prefer, GM's version of this part is an option.
5. Tachometer
A failing engine speed sensor could be the cause of numerous issues in your car. It is a crucial part of your Audi's transmission, since it relays information to the ECU about how fast or slow the car's crankshaft is turning. If the sensor fails, it will affect the performance of the transmission, as well as 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 directly to the ECU at pin T55/49 via a grey wire. The ECU uses this signal to control the flow of fuel and boost as well as timig. It also sends 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 examine the continuity between pins 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. It should show approximately 1000 ohms resistance between those two pins. This is a standard 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.