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 situated near the edges of the transmission above the flywheel ring gear. It transmits a signal to the ECU via a grey wire (T55/49) which is then sent to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located at the edges of the transmission, just above the flywheel ring. This sensor sends a signal via the grey wire to pin T55/49. The ECU then uses this information to control fuel, timig and boost. It also sends an alert to the G5 Tachometer within the instrument cluster.
The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft has reached TDC, and where the camshaft lies so that it can activate the spark and injectors.
If this sensor fails to function, the ECU will display a P00160 error message. This means that the Crank Shaft is out of line with the Intake Camshaft. It could also indicate a chain stretch or a jump in the chain link of the upper chain of timing. The code will not appear without the additional information supplied by other sensors (G4 or G40).
Testing is a bit challenging as there are two different connector pins, and they perform different functions but the best method to test it is by measuring resistance between the sensor and the ECU. When the sensor is fully operational, it should read approximately 1000 ohms. If audi a1 keys having issues with this sensor, look for evidence of oil or coolant in the connector bay.
2. Injectors
Yesterday accelerating full speed from highway paytoll i had a big cut in power like the engine is out of gas or the injectors are not firing any more. I took out the spark plugs this morning and found that 3 were soaked with gasoline and the 4th was dry. I placed a tissue over each injector hole and when I start the engine with no sparks, the ones with gazoline jump out. The 4th one stays closed. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 i get zero ohm. I think the issue is in another location.
I also tried to reset the PID without success. The car can start when the G28 is not plugged in and is running fine when it is plugged in however it has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even when unplugged, still shows a temperature of -49c. I also noticed that the gauge for oil pressure in the cockpit shows 2 bar when the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do. I feel like i've pretty much all other possibilities out. I'm concerned that i may have missed something. If anyone has any suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter is similar to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily find an extra in a wrecking shop or parts store. It is simple to test them - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's side). They must be infinite ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that needs to know the position and speed of the crankshaft 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 either of these sensors go wrong, you will receive codes on the diagnostic scanner which could cause engine shut down.
The signs of a malfunctioning G28 sensor include an inaccurate gearbox rev counter the gears are shifting faster than normal and/or misfiring when in gear. It is likely that your sensor is failing and needs to be replaced if you notice any of these symptoms. They are cheap and easy-to-find particularly in the case of a Bosch model like ours. Alternately, the GM version of this component is also a good choice.
5. Tachometer
A failing engine sensor could cause a myriad of issues in your car. It is an important part of the transmission of your Audi, as it transmits information to the ECU on how fast or slow the engine of the car is spinning. When this sensor fails, it will disrupt the performance of the transmission and the rest of the car's components.
The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It sends a signal via an uncolored wire to the ECU pin T55/49. The ECU then processes this signal to control fuel, timig, and boost and then 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. You can also check continuity between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. There should be the resistance to be around 1000 ohms between these points. This part is common across the Audi 80-100-200-RS2 model, ranging from the 1985 MC up to the 1997 UrS AN and 1995 RS2 DU, so you might find them in wrecking yards.