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 situated at the edge of transmission, above the flywheel gear. It sends a signal to the ECU via an uncolored wire (T55/49) and then to the tachometer within the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends a signal to ECU pin T55/49 via the grey wire. The ECU uses this information to control the amount of fuel and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.
The sensor is used to connect 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 start spark and injectors accordingly.
If this sensor fails, the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync and could indicate the chain stretching 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).
Testing is a bit tricky since there are two connector pins and they perform different functions however the best way to test it is by measuring resistance between the sensor and the ECU. It should read about 1000 ohms when the sensor is at full operation. Check for signs of coolant or oil in the connector bay if you have issues with this part.
2. Injectors
Yesterday accelerating full speed from highway paytoll, i experienced an abrupt drop in power like the engine is out of gas or the injectors aren't firing anymore. I took out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was dry. When i crank the engine with no sparks i put tissue on top of each injector hole and the 3 that were drenched in gazoline pop out, but the 4th stay shut. I tested the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. I assume that the problem 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 plugged in. However the intermittent misfire issue persists at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature value of -49c, even if I unplug it. I also noticed that the gauge for oil pressure 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, i believe that i've ruled out everything else. But i am afraid i might have missed something. Let me know if you have any ideas! TIA!
3. audi lost key replacement in the g28 gets a signal 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 which is why you can easily locate one at a wrecking yard or in a local parts store. Testing them is easy by putting 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 end). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that has to know the position and speed of the crankshaft to make decisions regarding fuel injector timing etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you encounter a problem with either one of these, the diagnostic scanner will show codes that could cause an engine shut down.
Some of the symptoms of a failing G28 sensor include an inaccurate rev counter for the gearbox, gears shifting quicker than normal and/or a misfire when you are in gear. If you have any of these issues it is most likely that your sensor is failing and should be replaced. The good news is that they are very affordable and readily available particularly if you're looking at an Bosch sensor, which is what ours are. You can also choose the GM version of this component is also a great option.
5. Tachometer
A damaged engine sensor could cause a variety of issues within your vehicle. It's a vital component of the Audi's transmission as it sends information to the ECU about how fast or slow the car's crankshaft is spinning. This sensor can cause the transmission to fail and other components of the car to be affected.
The G5 engine speed sensor is located at the outside of the transmission, above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49, via a grey wire. The ECU then uses and processes this signal to control fuel, timig and boost, and also transmitting it to the G5 Tachometer located in the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, 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 two points. This is a standard part across the Audi 80 100 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.