How to Replace audi key fob shows how to replace the G28 Engine Speed Sensor. This sensor is located on the edge of the transmission just above the flywheel ring gear. It transmits a signal to the ECU through the grey wire T55/49 and then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated on the outside of the transmission, just above the flywheel ring. This sensor sends signals through the grey wire to pin T55/49. The ECU uses this information to control boost and fuel. It also sends a signal to the G5 tachometer in the instrument cluster.
The sensor is used to link the G40 Camshaft position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is so it can trigger spark and injectors accordingly.
If this sensor fails, the ECU will display a P00160 error code. This means that the Crank Shaft is not in alignment 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 code will not appear on its own without additional information from other sensors (G4 and G40).
Testing can be a bit difficult since there are two connector pins, and they serve different purposes however the best method of testing it is by measuring resistance between the sensor and the ECU. When the sensor is fully operational, it should read about 1000 ohms. If you are having problems with this component, look for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at full speed I noticed a significant decrease in power. It was as if the engine had run out of gas. Or my injectors weren't firing. In the morning, i removed the spark plugs, three were soaked with gazoline and the fourth was dry. I put a piece of tissue over each injector hole and when I start the engine without 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 found zero ohm. I'm assuming that the issue is elsewhere.
I also tried to reset the PID but with no luck. The car will start when the G28 is disconnected, but it runs fine with the G28 connected. However, the intermittent misfire problem persists at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is 0.
I'm not sure what to do, but i believe that i've eliminated everything else. I'm worried that i might have missed something. Let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style transmitter is the same as the G4 and both are used in the 80, 100 200, UrS and RS2 cars which is why you can easily locate one at a junkyard or from a parts store. Testing them is easy 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 should be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines are equipped with an ECU that must know the position and speed of the crankshaft to make decisions regarding timing of the fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these goes wrong, you will receive codes on the diagnostic scanner that can cause the engine to shut down.
A damaged G28 sensor could result in an inaccurate speed counter for the gearbox and a gearbox which shifts more quickly than normal, and/or an unfire when in the gear. It is possible that your sensor is failing and needs to be replaced if you encounter any of these symptoms. The good news is they are very cheap and readily available particularly when you're looking at an Bosch sensor, which is what ours are. Alternately, the GM version of this unit is also a good choice.
5. Tachometer
A failing engine sensor could cause a number of problems within your vehicle. It's a vital component of the Audi's transmission because it communicates to the ECU about how fast or slow the car's crankshaft is spinning. This sensor could cause the transmission to malfunction and other car components to be affected.
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 through a grey wire. The ECU uses this signal to control the amount of fuel and boost, and also to timigrate. It also relays it to the G5 Tachometer in instrument cluster. You can check the sensor for failure by examining the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. It should show approximately 1000 ohms of resistance between those 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 so good ones might be availble in wrecking yards.