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 located near the edges of the transmission just above the flywheel ring gear. It sends a message to the ECU through a grey wire T55/49, then to the tachometer on the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the edge of transmission, directly above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU uses this information to regulate the amount of fuel and boost. It also sends a signal to the G5 Tachometer located in the instrument cluster.
The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must be aware of when the crankshaft has reached TDC, and the location of the camshaft so that it can activate the spark and injectors.
If this sensor fails to function, the ECU will display an error code P00160. This means that the Crank Shaft is out of alignment with the Intake Camshaft. It could also indicate an issue with the chain or a jumped chain link in the upper timing chain. However, the code won't appear on its own, without additional information from other sensors (G4 and G40).
audi a4 key replacement 's a bit tricky to test as there are various pins on the connector and they all have different functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. If the sensor is operational, it should be reading about 1000 ohms. Examine for signs of coolant or oil in the connector bay if you have issues with this component.
2. Injectors
Yesterday, when i was accelerating to the fullest speed from highway paytoll, i experienced massive power loss like the engine is out of gas or the injectors are not firing anymore. In the morning, i removed the spark plugs, three were drenched in gazoline, the fourth was dry. I put tissue over each injector hole and when i start the engine without sparks, the 3 with gazoline jump out. The 4th one stays shut. I tested the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. Therefore, i think the issue is elsewhere.
I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it is running fine with the G28 connected. However the intermittent misfire issue persists at higher RPM. The coolant sensor (G62), even when unplugged, still shows an ice temperature of -49c. Also, i noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.
I'm not sure what to do, but i think i've pretty much completely ruled out all other possibilities. I'm concerned that i may have missed something. If anyone has suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal by the RPM sensor. The GM-style sender is identical to the G4 and both function in the 80 100, 200, UrS and RS2 cars so you can easily find one at a wrecking yard or in a local parts store. It is simple to test them - simply switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines needs to know the speed and position of the crankshaft to make decisions regarding fuel injector timing, etc. To accomplish this, it makes use of 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 the engine shutting down.
A damaged G28 sensor could cause an inaccurate speed counter for your gearbox, a gearbox that shifts more quickly than normal, or a misfire in the gear. It is likely that your sensor is failing and requires to be replaced if you notice any of these symptoms. The good news is that they are very affordable and readily available particularly when you're looking at an Bosch model, which is what we have. Alternately, the GM version of this component is also a great option.
5. Tachometer
A malfunctioning engine speed sensor could be the cause of many problems in your car. It's an essential component of your Audi's transmission, since it relays information to the ECU about how fast or slow the car's crankshaft is turning. This sensor can cause the transmission to fail and other components of the car to be affected.
The G5 engine speed sensor is located on the edge of the transmission, above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 via an uncolored wire. The ECU then uses and processes the signal to control the flow of fuel, timig and boost and then sends it on to the G5 tachometer in the instrument cluster. You can test for sensor failure by examining the continuity of 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 and pin T26a/12. There should be an average resistance of 1000 ohms between these two points. This part is common across the Audi 80-100-200-RS2 model, ranging beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 DU, so you might find them in wrecking yards.