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 near the edges of the transmission above the flywheel ring gear. It transmits a signal to the ECU via a grey wire (T55/49) and then to the tachometer within the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated on the edge of transmission, above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU then uses this information to control fuel, timig and boost. It also sends an indication to the G5 tachometer in the instrument cluster.
The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must be aware of when the crankshaft has reached TDC and also the location of the camshaft to trigger the spark and injectors.
If this sensor fails, the ECU will throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync and could indicate chain stretch or a jumped link on the upper timing chain. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).
Testing can be a bit difficult as there are two different connector pins, and they perform different functions but the most effective method of testing it is by measuring resistance between the sensor and the ECU. It should read about 1000 ohms when it is in full operation. If you're having issues with this part, check for signs of coolant or oil in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at maximum speed I noticed a massive drop in power. replacement audi car key was as if the engine had run out of gas. Or my injectors were not firing. In the morning, i removed the spark plugs, three were soaked with gazoline and the fourth one was dry. I placed a tissue over each injector hole, and when i start the engine with no sparks, the 3 with gazoline jump right out. The 4th one remains shut. I tried to test the ground connections of ECU pins 14,30, and 48/55. I found 0ohm. I assume that the problem is elsewhere.
I also tried to reset the PID but without success. The car will start when the G28 is unplugged, and it works fine when the G28 plugged in. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62) even when unplugged, still shows a temperature of -49c. Also i noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 if i crank up the engine.
I don't know what to do. I believe that I've ruled everything else out. But i'm worried that I may have missed something. If anyone has any suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter is similar to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or a parts store. It is simple to test them - just switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They must be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to know both the position and speed of the crankshaft in order to make a decision about fuel injector timing, etc. To do this, it makes use of 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 cause an engine shut down.
The signs of a malfunctioning G28 sensor are an inaccurate rev counter for the gearbox and gears that shift faster than normal and/or misfiring when you're in gear. It is probable that your sensor is failing and requires to be replaced if you experience any of these symptoms. The good news is they are quite affordable and readily available, especially if you're looking at a Bosch unit which is what we have. You can also choose the GM version of this part is also a great option.
5. Tachometer
A faulty engine speed sensor could be the cause of many issues with your vehicle. It's an essential component of the transmission of your Audi because it relays information to the ECU about how fast or slowly the engine is turning. If this sensor fails, it could cause problems for the transmission as well as the other car's components.
The G5 engine speed sensor is situated on the outside of the transmission, above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49, via an uncolored wire. The ECU is then able to process this signal to control the flow of fuel, timig and boost, and also transmitting it to the G5 Tachometer located in the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see approximately 1000 ohms resistance between these two points. This is a typical 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.