How to Replace an Audi G28 Engine Speed Sensor
In this video Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. This sensor is situated near the transmission's edge just above the flywheel gear. It sends a message to the ECU through an uncolored wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated on the edge of transmission, just above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU then uses this information to control fuel, timig and boost. It also sends an indicator to the G5 Tachometer in instrument cluster.
The sensor is used to link the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft has reached TDC, and the position of the camshaft, so that it can activate the spark and injectors.
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 possibly indicating the chain is stretched or a jump link on the upper chain of timing. However, the code won't appear on its own without additional information from other sensors (G4 and G40).
It can be a bit difficult to test as there are several pins on the connector, and they all have different functions. The best method for doing this is to measure the resistance between the ECU and the sensor. When the sensor is functional, it should read approximately 1000 ohms. If you're having issues with this part, check for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at a high speed I noticed a significant drop in power. It was as if the engine had run out of gas. Or, my injectors weren't firing. This morning i pull out the spark plugs, 3 were drenched with gazoline the fourth one was dry. I put tissue over each injector hole, and when i start the engine with no sparks, the ones that have gazoline pop right out. The 4th one remains closed. I checked the ground connection of ECU pins 14,30 and 48/55. I found zero ohm. So i assume the problem is somewhere else.
I also tried to reset the PID without success. The car is able to start when the G28 is disconnected and is running fine when it is plugged in however it has intermittent misfire issues at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is 0.
I'm not sure what to do, but i believe that i've completely ruled out all other possibilities. I'm worried that i might have missed something. If anyone has any ideas please chime in! TIA!
3. lost my audi car keys in the g28 can be activated by a signal from the RPM sensor. The GM-style transmitter is similar to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find a spare in a wrecking shop or parts store. It is simple to test them to do - just put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector end up) and 2 (2nd from the left on the black connector's end). They should be infinite ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines needs to be aware of the speed and position of the crankshaft to make decisions regarding timing of fuel injectors, etc. 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 one of these, the diagnostic scanner will show codes that could lead to an engine shut down.
The signs of a failing G28 sensor are an inaccurate rev counter for the gearbox the gears are shifting faster than normal and/or a misfire when you're in gear. It is likely that your sensor is failing and requires to be replaced if you experience any of these signs. The good news is they are quite affordable and easily accessible, especially if you're looking at an Bosch sensor, like ours. Alternatively, GM's version of this part would be a good option.
5. Tachometer
A failing engine speed sensor could be the reason behind numerous problems in your vehicle. It's a vital component of the Audi's transmission because it communicates to the ECU about how fast or slow the car's crankshaft is rotating. This sensor could 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 sends a signal directly to the ECU at pin T55/49 through a grey wire. The ECU uses this signal to regulate fuel and boost, and also to timigrate. It also sends it to the G5 Tachometer in instrument cluster. You can check for sensor failure by examining the continuity from the sensor to the tachometer. Additionally, you can examine the continuity between pins 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 detect an average resistance of 1000 ohms between these two points. This is the same across the Audi 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 Du You may also find them in wrecking yards.