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 above the flywheel ring gear. It transmits a signal to the ECU through an uncolored wire T55/49, then to the tachometer on the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated on the edge of transmission, directly above the flywheel ring. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends an indicator to the G5 Tachometer in instrument cluster.
The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and the location of the camshaft so it can trigger spark and injectors accordingly.
If this sensor fails when it fails, the ECU will display a P00160 error code. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also indicate a chain stretch or a jumped chain link in the upper chain of timing. The code will not appear without the additional information supplied by other sensors (G4 or G40).
Testing is a bit tricky because there are two connector pins and they have different functions but the most effective way to test it is to measure the resistance between the sensor and the ECU. It should read around 1000 ohms if the sensor is in full operation. If you are having problems with this part, check for evidence of oil or coolant in the connector bay.
2. Injectors
Yesterday, while accelerating from the highway paytoll at full speed I noticed a significant decrease in power. It was like the engine had run out of gas. Or my injectors were not firing. I pulled out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was dry. When audi replacement key fob start the engine without sparks, I put a piece of tissue on top of each injector hole and the 3 that were drenched in gazoline pop out, but the 4th stays closed. I checked the ground connection on ECU pins 14/55,30/55 and 48/55 I get 0ohm. I assume that the problem is somewhere else.
I also tried to reset the PID but without success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However the intermittent misfire issue persists at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0.
I'm not certain what to do, i think i've pretty much eliminated everything else. However, i'm afraid that i might have missed something. If anyone has any suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal sent from 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 a spare in a wrecking shop or a parts store. It is simple to test them by putting your DMM in resistance mode and measure between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black connector's side). They must be infinite ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that needs to know the position and speed of the crankshaft to make decisions about timing of the fuel injector, for example. In order to do this it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go bad you will get codes on the diagnostic scanner that can lead to engine shutdown.
The signs of a failed G28 sensor include an inaccurate rev counter in the gearbox and gears that shift faster than normal and/or misfiring when you are in gear. It is probable that your sensor is failing and requires to be replaced if you encounter any of these symptoms. They are cheap and easy-to-find, especially in the case of a Bosch sensor like ours. Alternately, GM's version this component is an excellent choice.
5. Tachometer
A malfunctioning engine speed sensor could be the reason behind numerous issues in your vehicle. It's a vital component of the Audi's transmission since it relays information to the ECU about how fast or slow the vehicle's crankshaft is turning. If this sensor fails, it will cause problems for the transmission and the other car's components.
The G5 engine speed sensor is located at the edge of the transmission just above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49, via a grey wire. The ECU is then able to process this signal to control fuel, timig, and boost and then sends it on to the G5 tachometer inside the instrument cluster. You can check the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and 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 standard component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.