How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. The sensor is located at the top of the transmission above the flywheel ring gear. It sends a message to the ECU through the grey wire T55/49 and then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
The sensor is located at the edge of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends signals to ECU pin T55/49 via an uncolored wire. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends an indication to the G5 Tachometer in instrument cluster.
The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft reached TDC, and the position of the camshaft, to trigger the spark and injectors.
If this sensor fails, the ECU will throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync, possibly indicating the chain stretching or a jump link on the upper chain of timing. However the code will not appear on its own, without additional information from other sensors (G4 and G40).
Testing is a bit challenging since there are two pins for the connector and they serve different purposes but the most effective method to test it is by measuring resistance between the sensor and the ECU. When the sensor is fully operational, it should be reading about 1000 ohms. Look for evidence of coolant or oil in the connector bay if you have issues with this component.
2. Injectors
Yesterday accelerating full speed from highway paytoll i had an abrupt drop in power like the engine is running out of gas or injectors aren't firing anymore. Today, i pulled out the spark plugs. Three were drenched with gazoline the fourth one was dry. I put tissue over each hole in the injector and when I start the engine without sparks, the three that have gazoline pop right out. The 4th one stays closed. I tested the ground connection of ECU pins 14,30, and 48/55. I got 0ohm. I'm assuming the issue is somewhere else.
I also tried to reset the PID but with no luck. The car will start when the G28 is disconnected and it runs perfectly when it is connected but it still has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows an ice temperature of -49c. Also i noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.
I'm not certain what to do, i believe that i've completely ruled out all other possibilities. I'm afraid i may have missed something. If anyone has any suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style transmitter is similar to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily locate the spare in a salvage shop or a parts store. It is simple to test them - simply switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector's end facing up). how do i get a replacement key for my audi must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines must be aware of the speed and position of the crankshaft in order to make a decision about timing of the fuel injector, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you have a problem with either one of these, the diagnostic scanner will show the codes that could trigger the engine shutting down.
The signs of a failing G28 sensor include an inaccurate gearbox rev counter, gears shifting quicker than normal and/or misfiring when you are in gear. If you have any of these issues, it is likely that your sensor is failing and needs replacing. The good news is that they are very affordable and readily available particularly if you're looking at the Bosch sensor, which is what ours are. You can also choose the GM version of this part is also a great option.
5. Tachometer
A failing engine speed sensor could be the reason behind numerous issues with your vehicle. It's an essential component of the transmission of your Audi, as it transmits information to the ECU on how fast or slowly the engine is turning. This sensor can cause the transmission to malfunction and other components of the car to be affected.
The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It sends a signal via gray wire to ECU pin T55/49. The ECU is then able to process 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 determine if the sensor is in failure by checking continuity from the sensor to the tachometer. Also, you can check 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 approximately 1000 ohms resistance between those points. This is a typical part across the Audi 80 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.