How to Replace an
audi a3 spare key G28 Engine Speed Sensor
Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. This sensor is located on the edge of the transmission, above the flywheel ring gear. It sends a signal to the ECU via the grey wire (T55/49) and then to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the edge of transmission, directly 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 the flow of fuel, timig and boost. It also sends an alert to the G5 Tachometer located in the instrument cluster.
The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is located so that it can trigger spark and injectors in the right way.
If this sensor fails, the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft are not in sync and possibly indicating chain stretch or a jumped link on the upper timing chain. The code won't show without the additional information provided by other sensors (G4 or G40).
Testing can be a bit difficult as there are two different connector pins and they perform different functions but the best way to test it is to measure resistance between the sensor and the ECU. If the sensor is functional, it should read around 1000 ohms. If you're experiencing issues with this sensor, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at full speed I noticed a significant drop in power. It was like the engine was running out of gas. Or my injectors were not firing. I took out the spark plugs this morning, 3 were soaked in gasoline, and the fourth was dry. I put a piece of tissue over each hole in the injector and when i turn the engine on without sparks, the three with gazoline jump right out. The 4th one remains shut. I checked the ground connection of ECU pins 14,30 and 48/55. I found 0ohm. I'm assuming that the issue is somewhere else.
I also tried to reset the PID with no success. The car is able to start if the G28 is unplugged and runs fine when it is plugged in, but still has intermittent misfire issues at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value 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'm not sure what to do. I feel like i've pretty much eliminated everything else. I'm concerned that i may have missed something. Let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style sender is the same as the G4 and both function in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or at a parts store. It is simple to test them - just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector end facing up). They must be infinite ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines must be aware of the position and speed the crankshaft to determine timing of the fuel injector, etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go badly, you will see codes on the diagnostic scanner that could cause engine shut down.
A failing G28 sensor can cause an inaccurate gearbox speed counter and a gearbox which shifts more quickly than normal, or an unfire when in gear. If you are experiencing any of these problems, it is most likely that your sensor is failing and needs replacing. The good news is that they are very cheap and readily available, especially in the case of a Bosch sensor, which is what ours are. Alternately, GM's version this part would be a good option.
5. Tachometer
A failing engine sensor could cause a number of problems in your vehicle. It's a vital component of your
Audi Key Copy's transmission, because it communicates to the ECU about how the
car key replacement audi's crankshaft is rotating. If the sensor fails, it can cause problems for the transmission and the other car's components.
The G5 engine speed sensor is situated on the outside of the transmission just above the flywheel ring gear and transmits a signal to the ECU at pin T55/49, via a grey wire. The ECU utilizes this signal to regulate the flow of fuel and boost as well as timig. It also relays it to the G5 Tachometer located in the instrument cluster. You can test for sensor failure by examining the continuity of the sensor to the tachometer. You can also check 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. It should show around 1000 ohms of resistance between those two pins. This is a common feature across the
audi a1 key fob 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 some good ones in wrecking yards.
