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. The sensor is located near the edges 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 located on the instrument cluster.
1. audi lost key is situated on the outside of the transmission, just above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends an alert to the G5 Tachometer in 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 also the position of the camshaft, to trigger the spark and injectors.
If this sensor fails, the ECU will display an error code P00160. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also indicate a chain stretch or a jumped chain link in the upper chain of timing. The code won't show without the additional information provided by other sensors (G4 or G40).
It is a little tricky to test as there are different connector pins, 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 around 1000 ohms when the sensor is operating at its maximum. Examine for signs of coolant or oil in the connector bay if you have issues 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 running out of gas or the injectors are not firing any more. Today, i pulled out the spark plugs, three were soaked with gazoline and the fourth was dry. I placed a tissue over each hole in the injector and when i start the engine without sparks, the ones with gazoline jump out. The 4th one remains shut. I tested the ground connection of ECU pins 14,30 and 48/55. I found 0ohm. So i assume the problem is somewhere else.
I also tried to reset PID but without success. The car is able to start if the G28 is disconnected and is running fine when it is plugged in, but still has the intermittent misfire issue at higher RPM. The coolant sensor (G62), even when unplugged, still shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is 0.
I don't know what to do. I feel like i've pretty much all other possibilities out. However, i'm afraid that i might 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 transmitter is identical to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. It is easy to find an extra in a wrecking shop or a parts store. It is easy to test them: simply switch your DMM into resistance mode and measure 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 in our 20vt turbo (3B AAN ABY) engines must be aware of the position and speed the crankshaft to make decisions regarding timing of the fuel injector, etc. 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 show codes that could cause an engine shutdown.
Some of the signs of a failing G28 sensor are an inaccurate rev counter in the gearbox, gears shifting quicker than normal, and/or a misfire when in gear. It is probable that your sensor is failing and requires to be replaced if you encounter any of these signs. They're cheap and easy to find particularly in the case of an Bosch model like ours. Alternately, GM's version this component is an excellent choice.
5. Tachometer
A faulty engine speed sensor could be the cause of a slew of problems in your car. It's an essential component of the Audi's transmission since it relays information to the ECU about how fast or slow the car's crankshaft is spinning. This sensor can cause the transmission to malfunction and other car components to be affected.
The G5 engine speed sensor is located on the edge of the transmission above the flywheel ring gear and sends a signal to the ECU at pin T55/49 via a grey wire. The ECU is then able to process this signal to regulate the flow of 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 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 [79]) and between pin T6a/1 and pin T26a/12. You should detect a resistance of approximately 1000 ohms in these areas. 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.