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 outside of the transmission, above the flywheel gear. It transmits a signal the ECU via a grey wire (T55/49) which is then sent to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
The sensor is located at the edge of the transmission, above the flywheel ring gear G28 Engine Speed Sensor sends signals to ECU pin T55/49 via the grey wire. The ECU utilizes this information to control boost and fuel. It also sends signals to the G5 tachometer in the instrument cluster.
The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and the location of the camshaft so it can activate spark and injectors accordingly.
If this sensor fails to function, the ECU will display a P00160 error message. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also indicate an issue with the chain or a jumpy chain link in the upper chain. However the code will not be displayed on its own without additional information from other sensors (G4 and G40).
It's a bit tricky to test because there are different pins on the connector, and each one has different functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. It should read about 1000 ohms when it is at full operation. Look for signs of coolant or oil in the connector bay if you are experiencing issues with this component.
2. Injectors
Yesterday accelerating full speed from highway paytoll, i experienced a big cut in power like the engine is running out of gas or injectors are not firing anymore. I took out the spark plugs this morning and found that 3 were soaked in gasoline, and the fourth was unclean. When i crank the engine with no sparks i put tissue on top of each injector hole and the 3 drenched with gazoline pop out, but the 4th stay shut. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 I got 0ohm. I think the issue is somewhere else.
I also tried to reset the PID but without success. The car is able to start if the G28 is not plugged in and runs fine when it is connected, but still has intermittent misfire issues at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature of -49c even when i unplug it. Also, i noticed that the oil pressure gauge in the cockpit shows 2 bar when the actual pressure is 0.0 when I crank up the engine.
I'm not certain what to do, but i feel i have pretty much completely ruled out all other possibilities. But i am afraid I might have missed something. If anyone has any suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal from the RPM sensor. The GM-style sensor is identical to the G4 and they both work in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or in a local parts store. It is easy 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 end facing up). They should be infinite Ohms.
4. ECU
audi a3 key replacement thekeylab.co.uk (3B, AAN, ABY and ADU) engines have an ECU that has to know the position and speed of the crankshaft in order to make a decision about timing of the fuel injector, for example. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes bad you will get codes on the diagnostic scanner which could cause engine shut down.
The signs of a failed G28 sensor include an inaccurate gearbox rev counter, gears shifting quicker than normal and/or misfiring when you are in gear. It is possible that the sensor is failing and needs to be replaced if you encounter any of these symptoms. The good news is they are very affordable and readily available, especially if you're looking at an Bosch sensor, which is what ours are. You can also choose the GM version of this part is also a good option.
5. Tachometer
A malfunctioning engine speed sensor could be the cause of a slew of issues with your vehicle. It's a crucial component of the transmission in your Audi, as it transmits information to the ECU on how fast or slowly the engine is spinning. If the sensor fails, it will cause problems for the transmission as well as 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 transmits a signal to the ECU at pin T55/49 via an uncolored wire. The ECU then processes this signal to regulate fuel, timig and boost, and also transmitting it to the G5 tachometer inside the instrument cluster. You can determine if the sensor is in failure by examining the continuity from the sensor to the tachometer. Also, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]) and between pin T6a/1 and pin T26a/12. It should show around 1000 ohms of resistance between those points. This is a standard part that is found across the Audi 80, 100 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.