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. The sensor is located on the edge of the transmission just above the flywheel ring gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated on the edge of transmission, just above the flywheel ring. This sensor sends signals through the grey wire to pin T55/49. The ECU utilizes this information to regulate the amount of fuel and boost. It also sends signals to the G5 tachometer inside the instrument cluster.
The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu has to be aware of when the crankshaft has reached TDC and also where the camshaft lies to trigger the spark and injectors.
If this sensor fails the ECU will show a P00160 code which means the Crank Shaft and Intake Camshaft are not in sync and possibly indicating the chain stretching or a jump link on the upper timing chain. The code won't appear without the additional information provided by other sensors (G4 or G40).
Testing is a bit tricky since there are two connector pins, and they serve different purposes but the best method of testing it is to measure resistance between the sensor and the ECU. When the sensor is operational, it should read around 1000 ohms. If you're experiencing issues with this component, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, while accelerating from the highway paytoll at a high speed I noticed a massive reduction in power. It was like the engine had run out of gas. Or, my injectors weren't firing. This morning i pull out the spark plugs, three were drenched in gazoline, the 4th one was dry. When I start the engine, there are no sparks i put tissue on the top of each of the injector holes and the 3 that were drenched in gazoline jump out but the 4th one stays shut. I tested the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. So i assume the problem is in another place.
I also tried to reset the PID but with no luck. The car will start when the G28 is disconnected and it runs perfectly when it is connected but it still is experiencing intermittent misfires at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature of that check here is -49c even after unplugging 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 sure what to do. I believe that I've ruled everything else out. I'm concerned that i may have missed get more info something. If anyone has any suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal by the RPM sensor. The GM-style sensor is the same as the G4 and both are used in the 80, 100, 200, UrS and RS2 cars so you can easily find one at a salvage yard or in a local parts store. It is easy to test them: simply switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They should be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines are equipped with an ECU that has to know the speed and position of the crankshaft in order to make decisions regarding fuel injector timing etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either one of these, 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 or a gearbox that shifts more quickly than normal, or an unfire when in gear. It is probable that the sensor is failing and needs to be replaced if you encounter any of these symptoms. The good news is that they are very affordable and easy to find, especially in the case of a Bosch unit which is what we have. If you prefer, GM's version of this part is a good option.
5. Tachometer
A failing engine speed sensor could be the reason behind many issues in your car. It's a crucial component of the transmission in your Audi, as it transmits information to the ECU about how fast or slow the car's engine is turning. This sensor could cause the transmission to fail and other car components to be affected.
The G5 engine sensor is located at the edge of the transmission, over the flywheel ring. It transmits an electrical signal through an uncolored wire to the ECU pin T55/49. The ECU uses this signal to read more control the flow of fuel and boost as well as timig. It also sends it more info to the G5 Tachometer in instrument cluster. You can test the sensor for any failure by checking the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should observe approximately 1000 ohms of resistance between those points. This part is common across the Audi 80-100-200-RS2 series, starting beginning with the check here 1985 MC and up to the 1997 UrS An and 1995 RS2 Du You may also find them in wrecking yards.