How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. This sensor is located near the edges of the transmission, above the flywheel ring gear. It sends a message to the ECU via a grey wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located at the edges of the transmission, above the flywheel ring. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU utilizes this information to regulate fuel and boost. It also sends an indication to the G5 tachometer in the instrument cluster.
The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can start spark and injectors accordingly.
If this sensor fails the ECU will show a P00160 code which means the Crank Shaft and Intake Camshaft are out of sync and possibly indicating the chain is stretched or a jump link on the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40).
Testing is a bit tricky because there are two connector pins, and they serve different purposes however the best way to test it is by measuring resistance between the sensor and the ECU. It should read approximately 1000 ohms when the sensor is operating at its maximum. Examine for signs of coolant, or oil in the connector bay if you are experiencing issues with this component.
2. My Web Site , while accelerating at full speed from the highway paytoll, I experienced an abrupt drop in power like the engine is running out of gas or the injectors are not firing anymore. This morning i pull out the spark plugs, 3 were soaked with gazoline and the fourth one was dry. I placed a tissue over each injector hole, and when I start the engine without sparks, the 3 that have gazoline pop right out. The fourth one remains closed. I tested the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. I think the issue is in another location.
I also tried to reset the PID without success. The car is able to start if the G28 is disconnected and runs fine when it is connected however it has intermittent misfire issues at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value -49c, even if I unplug it. Also i noticed that the gauge for oil pressure 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, as i believe that i've completely ruled out all other possibilities. However, i'm afraid that I might have missed something. Please let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter is identical to the G4 and both function 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 simple to test them - just 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
The ECU of our 20vt turbo (3B AAN ABY) engines requires to know both the speed and position of the crankshaft to determine timing of the fuel injector, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If audi replacement car keys of these go wrong, you will receive codes on the diagnostic scanner that can cause the engine to shut down.
A malfunctioning G28 sensor could result in an inaccurate speed counter for the gearbox or a gearbox that shifts faster than normal, and/or a misfire in the gear. It is likely that the sensor is failing and needs to be replaced if you notice any of these symptoms. The good news is they are quite affordable and readily available particularly in the case of the 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 failing engine sensor could cause a variety of issues in your vehicle. It is an important part of the transmission of your Audi because it relays information to the ECU about how fast or slowly the engine of the car is turning. This sensor could cause the transmission to malfunction and other components of the car to be affected.
The G5 engine speed sensor is located on the outside of the transmission just above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 via a grey wire. The ECU then uses and processes this signal to control the flow of fuel, timig and boost, and also sends it on to the G5 Tachometer located in 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 on pin T6a/1 (trace [79]) as well as between T6a/1, and the instrument cluster 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 series, starting beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 Du So, you may find some good ones in wrecking yards.