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 situated at the top of the transmission just above the flywheel ring gear. It transmits a signal to the ECU via an uncolored wire (T55/49) which is then sent to the tachometer within the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission above the flywheel ring gear the G28 Engine Speed Sensor sends signals to ECU pin T55/49 using the grey wire. The ECU then uses this information to control the boost, fuel, and timig. 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 is TDC and where the camshaft is located so that it can start spark and injectors according to the situation.
If this sensor fails, the ECU will display a P00160 error code. This means that the Crank Shaft is not in alignment with the Intake Camshaft. It could also be a sign of an issue with the chain or a jumpy chain link in the upper chain of timing. However, the code won't be displayed on its own without additional information from other sensors (G4 and G40).
Testing is a bit tricky as there are two different connector pins and they serve different purposes but the most effective method of testing it is to measure the resistance between the sensor and the ECU. If the sensor is operational, it should read around 1000 ohms. If you are having problems with this part, check for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at full speed I noticed a massive reduction in power. audi car key was as if the engine was running out of gas. Or my injectors were not firing. In the morning, i removed the spark plugs. Three were drenched in gazoline, the 4th one was dry. I placed a tissue over each injector hole and when I start the engine without sparks, the ones that have gazoline pop right out. The 4th one remains shut. I tested the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. I assume that the problem is in another location.
I also tried to reset the PID without success. The car will start when the G28 is not plugged in and is running fine when it is plugged in, but still is experiencing intermittent misfires at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value -49c even when i unplug it. Also i noticed that the oil pressure gauge in the cockpit is showing 2 bar while the actual pressure is 0.0 when I crank up the engine.
I'm not sure what to do. I believe that I've eliminated everything else. I'm worried that i might have missed something. If anyone has any ideas please chime in! TIA!
3. Fuel Pump
The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style transmitter is similar to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or parts store. It is easy to test them - just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines have an ECU that must know the speed and position of the crankshaft to make decisions about timing of the fuel injector, for example. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these go bad you will get codes on the diagnostic scanner that can lead to engine shutdown.
A failing G28 sensor can cause an inaccurate gearbox speed counter, a gearbox that shifts faster than normal, or a misfire while in the gear. If you are experiencing any of these issues it is likely that your sensor is deteriorating and needs replacing. They're inexpensive and easy to locate especially if they're an Bosch sensor like ours. Alternatively, GM's version of this part is an excellent choice.
5. Tachometer
A malfunctioning engine sensor can cause a myriad of issues in your vehicle. It's a crucial component of the transmission in your Audi, as it transmits information to the ECU regarding how fast or slow the engine of the car is spinning. When this sensor fails, it can affect the performance of the transmission and the rest of the car's components.
The G5 engine speed sensor is located at the edge of the transmission above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 through a grey wire. The ECU uses this signal to control the flow of fuel and boost as well as timig. It also transmits it to the G5 Tachometer inside the instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should see the resistance to be around 1000 ohms between these two points. This is a common feature across the Audi 80-100-200-RS2 model, ranging from the 1985 MC all the way up to the 1997 UrS AN and 1995 RS2 Du You may also find good ones in wrecking yards.