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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 on the edge 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 located on the instrument cluster.
1. Engine Speed Sensor
The grey wire is located at the edges of the transmission, directly above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU uses this information to regulate the amount of fuel and boost. It also sends an indicator to the G5 Tachometer in instrument cluster.
The sensor is used as a reference for comparing with 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 activate spark and injectors accordingly.
If audi q5 locked keys in car fails, the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync and could indicate the chain is stretched or a jump link on the upper timing chain. The code won't show without the additional information provided by other sensors (G4 or G40).
Testing is a bit tricky as there are two different pins for the connector and they perform different functions but the most effective way to test it is to measure resistance between the sensor and the ECU. It should read approximately 1000 ohms when it is in full operation. If you're having issues with this part, check for signs of coolant or oil in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at full speed I noticed a massive decrease in power. It was like the engine was running out of gas. Or my injectors were not firing. Today, i pulled out the spark plugs, 3 were soaked with gazoline and the fourth one was dry. When i crank the engine with no sparks, i place a tissue on top of each injector hole and the 3 that were drenched in gazoline leap out, however the 4th stays closed. I checked the ground connection of ECU pins 14,30 and 48/55. I found zero ohm. So i assume the problem is elsewhere.
I also tried to reset PID without success. audi q5 locked keys in car can start if the G28 is not plugged in and it runs perfectly when it is connected, but still has intermittent misfire issues at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value -49c, even if I unplug it. I also noticed that the oil pressure gauge in the cockpit is showing 2 bar while the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do, i believe that i've completely ruled out all other possibilities. However, i'm afraid that I may have missed something. Please let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter functions similarly to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. It is easy to find an extra in a wrecking shop or a parts store. Testing them is easy to do - just put your DMM in resistance mode and take measurements 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 should be infinite ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines needs to be aware of the speed and position of the crankshaft in order to make a decision about timing of the fuel injector, etc. To accomplish this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go badly, you will see codes on the diagnostic scanner that can cause the engine to shut down.
Some of the signs of a failed G28 sensor are an inaccurate gearbox rev counter 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 needs to be replaced if you encounter any of these signs. The good thing is that they are very cheap and easy to find, especially if you're looking at an Bosch model, like ours. Alternately, the GM version of this unit is also a good choice.
5. Tachometer
A malfunctioning engine sensor can cause a variety of issues in your car. It's an essential component of the transmission of your Audi because it relays information to the ECU on how fast or slowly the engine of the car is spinning. When this sensor fails, it will disrupt the performance of the transmission and the other car's components.
The G5 engine speed sensor is located on the outside of the transmission, above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 via a grey wire. The ECU uses this signal to regulate fuel and boost, as well as timig. It also transmits it to the G5 Tachometer located in the instrument cluster. You can test for sensor failure by examining the continuity of the sensor to the tachometer. You can also verify continuity between pin 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 see around 1000 ohms of resistance between those points. This is the same across the Audi 80-100-200-RS2 model, ranging from the 1985 MC up to the 1997 UrS An and 1995 RS2 Du So, you may find good ones in wrecking yards.