How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is situated near the edges of the transmission just above the flywheel ring gear. It transmits a signal the ECU via an uncolored wire (T55/49) and then to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated on the edge of transmission, above the flywheel ring. The sensor sends an electrical signal 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 indication to the G5 Tachometer within the instrument cluster.
The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and the location of the camshaft so it can activate spark and injectors in the right way.
If this sensor fails, the ECU will show a P00160 code which means the Crank Shaft and Intake Camshaft are not in sync and could indicate chain stretch or a jumped link on the upper timing chain. The code will not appear without the additional information supplied by other sensors (G4 or G40).
It's a bit tricky to test since there are various pins on the connector and each one has different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. It should read about 1000 ohms when it is at full operation. If you are having problems with this sensor, look for signs of coolant or oil in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at full speed I noticed a massive drop in power. It was like the engine was running out of gas. Or, my injectors were not firing. In the morning, i removed the spark plugs, 3 were drenched in gazoline, the fourth was dry. I placed a tissue over each injector hole, and when I turn the engine on without sparks, the 3 with gazoline jump right out. The fourth one remains shut. I inspected the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got zero Ohm. I'm assuming that the issue is in another location.
I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it is running fine with the G28 connected. However, the intermittent misfire problem still occurs at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature of -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is 0.
I'm not certain what to do, i believe that i've eliminated everything else. I'm concerned that i may have missed something. Let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style sender is the same as the G4 and they both work in the 80 100 200, UrS and RS2 cars so you can easily find one at a wrecking yard or from a parts store. Test them out to do - just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black connector's end). They should be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines needs to know both the position and speed click here the crankshaft to make decisions regarding fuel injector timing, etc. To do this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either of these sensors, the diagnostic scanner will display the codes that could trigger an engine shut down.
Some of the signs of a failing G28 sensor include an inaccurate rev counter in the gearbox and gears that shift faster than normal, and/or a misfire when in gear. It is possible that the sensor is failing and needs to be replaced if you notice any of these signs. They are cheap and easy-to-find particularly in the case of an Bosch unit like ours. Alternately, the GM version of this component is also a good option.
5. Tachometer
A faulty engine speed sensor could be the cause of a slew of problems in your vehicle. It is an important part of the transmission in your Audi since it sends information click here to the ECU regarding how fast or slow the car's engine is turning. This sensor here can cause the transmission to fail and other components in the car to be affected.
The G5 engine sensor is located at the outskirts of the transmission, just above the flywheel ring. It transmits an electrical signal through a audi tt keys gray wire to the ECU pin T55/49. The ECU then uses and processes this signal to regulate fuel, timig and boost and then sends it on to the G5 Tachometer located in the instrument cluster. You can check 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 on pin T6a/1 (trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should detect a resistance of approximately 1000 ohms between these two points. This part is common across the Audi 80-100-200-RS2 series, starting from audi convenience key the 1985 MC all the way up to the 1997 UrS An and 1995 RS2 DU You may also find some good ones in wrecking yards.