How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows you 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 via a grey wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the edge of transmission, just above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends a signal 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 know 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 display a P00160 code which means the Crank Shaft and Intake Camshaft aren't in sync, possibly indicating the chain is stretched or a jump link on the upper chain of timing. However, the error code won't appear on its own without additional information from other sensors (G4 and G40).
It is a little tricky to test since there are different connector pins, and each one has different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. If the sensor is operational, it should read approximately 1000 ohms. Check for signs of coolant or oil in the connector bay if you have issues with this component.
2. Injectors
Yesterday, while accelerating from the highway paytoll at maximum speed I noticed a massive reduction in power. It was as if the engine was running out of gas. Or, my injectors were not firing. I pulled out the spark plugs this morning and found that 3 were soaked with gasoline and the fourth was dry. I placed a tissue over each hole in the injector and when i start the engine with no sparks, the three that have gazoline pop right out. The fourth one remains closed. I checked the ground connection on ECU pins 14/55,30/55 and 48/55 I got zero Ohm. I'm assuming that the issue is in another location.
I also tried to reset PID without success. The car is able to start if the G28 is not plugged in and it runs perfectly when it is connected, but still has intermittent misfire issues at higher RPM. The coolant sensor (G62) even when it is unplugged, shows an ice temperature of -49c. I also noticed that the gauge for oil pressure in the cockpit shows 2 bar while the actual pressure is 0.0 when I crank up the engine.
I'm not sure what to do, but i think i've pretty much ruled out everything else. However, i'm afraid that I may have missed something. If anyone has suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style transmitter is identical to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily locate the spare in a salvage shop or parts store. It is simple to test them - just switch your DMM into resistance mode and determine 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) engines needs to be aware of the position and speed of the crankshaft to determine timing of the fuel injector, etc. In order 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 sensors, the diagnostic scanner will show the codes that could trigger an engine shutdown.
A malfunctioning G28 sensor could cause an inaccurate speed counter for the gearbox, a gearbox that shifts faster than normal, or a misfire in gear. If you are experiencing any of these issues it is likely that your sensor is failing and requires replacement. The good thing is that they are very cheap and readily available, especially in the case of the Bosch unit which is what ours are. Alternatively, GM's version of this component is an excellent choice.
5. Tachometer
A failing engine speed sensor could be a cause for a slew of issues in your vehicle. It is an important part of the transmission of your Audi since it sends information to the ECU on how fast or slowly the car's engine is spinning. If the sensor fails, it will disrupt the performance of the transmission and the other car's components.
The G5 engine speed sensor is located at the outside of the transmission above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 through a grey wire. The ECU then processes the signal to control the flow of fuel, timig and boost as well as transmitting it to the G5 tachometer in the instrument cluster. audi replacement key uk can check the sensor for any failure by checking the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. There should be an average resistance of 1000 ohms between these points. This is the same across the Audi 80-100-200-RS2 range, from the 1985 MC all the way up to the 1997 UrS AN and 1995 RS2 DU, so you might find some good ones in wrecking yards.
