How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is situated on the edge of the transmission just above the flywheel ring gear. It sends a message to the ECU through an uncolored wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
The grey wire is located at the edges of the transmission, directly above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU uses this information to control fuel and boost. It also sends an alert to the G5 Tachometer within the instrument cluster.
The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to 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 the P00160 error, which means the Crank Shaft and Intake Camshaft are out of sync and could indicate chain stretch or a jumped link on the upper chain of timing. However, the error code won't be displayed on its own without additional information from other sensors (G4 and 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. It should read approximately 1000 ohms when the sensor is in full operation. If you're experiencing issues with this part, check for evidence of oil or coolant in the connector bay.
2. More Tips , when accelerating from highway paytoll at maximum 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, 3 were soaked in gasoline, and the fourth was dry. I placed a tissue over each injector hole and when I turn the engine on without sparks, the 3 with gazoline jump right out. The 4th one remains closed. I checked the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got zero ohm. I assume that the problem is somewhere else.
I also tried to reset the PID but with no luck. The car is able to start when the G28 is not plugged in and is running fine when it is plugged in but it still has the intermittent misfire issue at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows temperatures of -49c. Also, i noticed that the gauge for oil pressure in the cockpit shows 2 bar, whereas the actual pressure is 0.0 if i crank up the engine.
I'm not certain what to do, i believe that i've eliminated everything else. But i'm worried that I might have missed something. Please let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal 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. You can easily locate the spare in a salvage shop or 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's end facing up). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines requires to know both the position and speed the crankshaft to make decisions regarding timing of fuel injectors, etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go wrong, you will receive codes on the diagnostic scanner which could cause engine shut down.
Some of the signs of a failing G28 sensor include an inaccurate gearbox rev counter and gears that shift faster than normal, and/or a misfire when you are in gear. If you have any of these problems, it is likely your sensor is failing and requires replacement. The good thing is that they are very cheap and easy to find, especially if you're looking at a Bosch unit which is what ours are. Alternatively, GM's version of this part would be an option.
5. Tachometer
A failing engine speed sensor could be the reason behind numerous issues with your car. It's a vital component of the Audi's transmission because it communicates to the ECU about how fast or slow the vehicle's crankshaft is turning. If this sensor fails, it will affect the performance of the transmission as well as the rest of the car's components.
The G5 engine sensor is located near the edge of transmission, above the flywheel ring. It transmits signals via gray wire to ECU pin T55/49. The ECU uses this signal to control the amount of fuel and boost, as well as timig. It also transmits it to the G5 Tachometer inside the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [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 the same across the Audi 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS An and 1995 RS2 Du You may also find some good ones in wrecking yards.