How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. The sensor is located at the edge of transmission over the flywheel gear. It sends a message to the ECU via the grey wire T55/49 and then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the outside of the transmission, just above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then uses this information to control fuel, timig and boost. It also sends signals to the G5 tachometer inside the instrument cluster.
The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft has reached TDC, and the location of the camshaft in order to activate the spark and injectors.
If this sensor fails, the ECU will display a P00160 error code. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also be a sign of a chain stretch or a jumped chain link in the upper chain of timing. lost my audi car keys won't show without the additional information supplied by other sensors (G4 or G40).
It is a little tricky to test since there are different pins on the connector and each has its own functions. The best way to do it is by measuring the resistance between the ECU and the sensor. It should read about 1000 ohms when the sensor is in full operation. If you're having issues with this component, look for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at maximum speed I noticed a massive drop in power. It was as if the engine had run out of gas. Or my injectors weren't firing. Today, i pulled out the spark plugs, three were drenched in gazoline, the fourth one was dry. I put tissue over each hole in the injector and when I start the engine with no sparks, the 3 with gazoline jump out. The 4th one remains shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found zero ohm. Therefore, i think the issue is somewhere else.
I also tried to reset the PID without success. The car will start when the G28 is disconnected, but it runs fine with the G28 connected. However the intermittent misfire issue persists at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature of that is -49c even after unplugging it. I also noticed that the gauge for oil pressure in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.
I don't know what to do. I believe that I've all other possibilities out. I'm concerned that i may have missed something. If anyone has suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal from the RPM sensor. The GM-style sender is identical to the G4 and they both work in the 80, 100 200, UrS and RS2 cars so you can easily find one at a junkyard or from a parts store. It is easy to test them - just switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They should be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines have an ECU that needs to know the position and speed of the crankshaft to make decisions about timing of the fuel injector, for example. To do this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these sensors, the diagnostic scanner will display codes that could lead to the engine shutting down.
Some of the signs of a malfunctioning G28 sensor include an inaccurate rev counter in the gearbox and gears that shift faster than normal, and/or a misfire when in gear. If you have any of these issues it is most likely that your sensor is deteriorating and requires replacement. They're cheap and easy to find especially in the case of a Bosch unit like ours. If you prefer, GM's version of this part is a good option.
5. Tachometer
A failing engine sensor could cause a myriad of issues within your vehicle. It's an essential component of the transmission in your Audi, as it transmits information to the ECU about how fast or slow the engine of the car is turning. This sensor could cause the transmission to malfunction and other car components 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 the signal to control fuel, timig, and boost and then transmitting it to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by examining the continuity of the sensor to the tachometer. You can also verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 and pin T26a/12. There should be a resistance of approximately 1000 ohms between these two points. This is a common feature across the Audi 80-100-200-RS2 range, from the 1985 MC all the way up to the 1997 UrS AN and 1995 RS2 Du, so you might find good ones in wrecking yards.