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. This sensor is situated at the edge of transmission just above the flywheel 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 located on the outside of the transmission, above the flywheel ring. The sensor transmits an electrical signal through the grey wire to pin T55/49. The ECU uses this information to control the amount of fuel and boost. It also sends signals to the G5 Tachometer located in the instrument cluster.
The sensor is used to connect the G40 Camshaft position Sensor. The ecu must know when the crankshaft reached TDC, and where the camshaft lies in order to activate the spark and injectors.
If this sensor fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is out of line with the Intake Camshaft. It could also indicate an issue with the chain or a jumped chain link in the upper chain of timing. The code will not appear without the additional information provided by other sensors (G4 or G40).
It's a bit tricky to test since there are different connector pins, and they all have different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. If the sensor is operational, it should be reading approximately 1000 ohms. Check for signs of coolant or oil in the connector bay if you are experiencing issues with this part.
2. Injectors
Yesterday, while accelerating at full speed from the highway paytoll, i experienced a big cut in power like the engine is running out of gas or the injectors are not firing at all. I took out the spark plugs this morning, three were drenched in gasoline and the 4th was dry. When i crank the engine without sparks i put tissue on top of each injector hole and the 3 that were drenched in gazoline jump out but the 4th one stays closed. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. i get zero ohm. I'm assuming the issue is in another place.
I also tried to reset the PID but without success. The car will start when the G28 is disconnected, but it works fine when the G28 more info plugged in. However, the intermittent misfire problem persists at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows a temperature of -49c. Also i noticed that the oil pressure gauge in the cockpit is showing 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. I'm worried that i might have missed something. If anyone has any ideas please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal sent from the RPM sensor. The GM-style transmitter is identical to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or parts store. Test them out to do - just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black connector's side). They should be infinite Ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that needs to know the speed and position of the crankshaft in order to make decisions regarding fuel injector here timing etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you have a problem with either of these sensors, the diagnostic scanner will show here codes that spare audi key could cause an engine shut down.
A failing G28 sensor could result in an inaccurate speed counter for your gearbox, a gearbox that shifts faster than normal, or a misfire while in the gear. It is likely that your sensor is failing and needs to be replaced if you experience any of these signs. They're inexpensive and easy to locate, especially when they're a Bosch unit like ours. If you prefer, GM's version of this part would be an option.
5. Tachometer
A failing engine sensor could cause a number of problems in your vehicle. It's an essential component of the transmission in your Audi, as it transmits information to the ECU regarding how fast or slowly the car's engine is spinning. This sensor can cause the transmission to malfunction and other car components to be affected.
The G5 engine speed sensor is located on the edge of the transmission, above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49, via an uncolored wire. The ECU then uses and processes the signal to control fuel, timig and boost, and also sends it on to the G5 tachometer in the 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]) as well as between T6a/1, and the instrument cluster pin T26a/12. It should show approximately 1000 ohms of resistance between these two points. This is a common feature across the Audi 80-100-200-RS2 series, starting from the 1985 MC here all the way up to the 1997 UrS An and 1995 RS2 DU, so you might find good ones in wrecking yards.