What Is Audi G28? History Of Audi G28
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 at the top of the transmission above the flywheel ring gear. It sends a message to the ECU via a grey wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated at the edges of the transmission, above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU then uses this information to control the boost, fuel, and timig. It also sends an indication to the G5 tachometer inside the instrument cluster.
The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can start spark and injectors according to the situation.
If this sensor fails, the ECU will show a P00160 code which means the Crank Shaft and Intake Camshaft are out of sync, possibly indicating chain stretch or a jumped link on the upper timing chain. However the code will not appear on its own, without additional information from other sensors (G4 and G40).
It's a bit tricky to test because there are several pins on the connector and they all have different functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. If the sensor is operational, it should be reading about 1000 ohms. Look for signs of coolant or oil in the connector bay if you are experiencing issues with this part.
2. Injectors
Yesterday accelerating full speed from highway paytoll i had an abrupt drop in power like the engine is running out of gas or injectors aren't firing anymore. I pulled out the spark plugs this morning, 3 were soaked with gasoline and the fourth was dry. I put a piece of tissue over each hole in the injector and when I turn the engine on without sparks, the ones that have gazoline pop right out. The 4th one stays closed. I tested the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. I assume that the problem is in another location.
I also tried to reset the PID without success. The car is able to start if the G28 is not plugged in and runs fine when it is plugged in, but still has intermittent misfire issues at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value -49c, even if I unplug it. Also, audi replacement key noticed that the oil pressure gauge in the cockpit is showing 2 bar while the actual pressure is 0.0 when i rev the engine.
I'm not certain what to do, but i think i've pretty much eliminated everything else. But i am afraid i might have missed something. Please let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal sent by the RPM sensor. The GM-style sender is identical to the G4 and they both work in the 80 100, 200, UrS and RS2 cars so you can easily find one at a junkyard or in a local parts store. It is simple to test them: simply put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector end facing up). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that has to be aware of the speed and position of the crankshaft in order to make a decision about fuel injector timing etc. To accomplish this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go wrong, you will receive codes on the diagnostic scanner that can lead to engine shutdown.
Some of the signs of a failed G28 sensor are an inaccurate rev counter for the gearbox the gears are shifting faster than normal and/or a misfire when in gear. If you are experiencing any of these issues, it is likely that your sensor is going bad and should be replaced. The good news is that they are very cheap and easily accessible particularly when you're looking at a Bosch unit which is what we have. You can also choose the GM version of this unit is also a great option.
5. Tachometer
A malfunctioning engine sensor can cause a variety of issues in your vehicle. It is a crucial part of the Audi's transmission as it sends information to the ECU about how fast or slow the vehicle's crankshaft is turning. This sensor can cause the transmission to fail and other components of the car to be affected.
The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It transmits a signal via gray wire to ECU pin T55/49. The ECU then uses and processes the signal to control the flow of fuel, timig and boost, and also sends it on to the G5 Tachometer located in the instrument cluster. You can check for sensor failure by examining the continuity of the sensor to the tachometer. Also, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 as well as pin T26a/12. You should observe approximately 1000 ohms of resistance between those points. This is the same across the Audi 80-100-200-RS2 series, starting from the 1985 MC up to the 1997 UrS An and 1995 RS2 DU So, you may find them in wrecking yards.