Audi G28: 10 Things I'd Like To Have Known Sooner
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In this video Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. The sensor is located near the transmission's edge, above the flywheel gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the edge of transmission, just above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU utilizes this information to control the amount of fuel and boost. It also sends signals to the G5 tachometer in the instrument cluster.
The sensor is used to link the G40 Camshaft position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is so it can trigger spark and injectors in the right way.
If this sensor fails when it fails, the ECU will display a P00160 error code. This indicates that the Crank Shaft is not in alignment with the Intake Camshaft. It could also be a sign of an issue with the chain or a jumped chain link in the upper chain of timing. The code will not appear without the additional information provided by other sensors (G4 or G40).
It's a bit tricky to test since there are various connector pins, and each has its own functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. When the sensor is fully operational, it should read about 1000 ohms. Check for signs of coolant, or oil in the connector bay if you have issues with this part.
2. Injectors
Yesterday, while accelerating from the highway paytoll at maximum speed I noticed a massive drop in power. It was like the engine was running out of gas. Or my injectors were not firing. In the morning, i removed the spark plugs, three were drenched in gazoline, the fourth was dry. When I crank the engine, there are no sparks i put tissue on the top of each of the injector holes and the 3 that were drenched in gazoline jump out but the 4th stays closed. I tried to test the ground connections 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 when the G28 is unplugged and it runs perfectly when it is plugged in but it still has intermittent misfire issues at higher RPM. The coolant temperature sensor (G62) shows the wrong temp value that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is 0.
I'm not certain what to do, i think i've pretty much eliminated everything else. However, i'm afraid that I may have missed something. Please let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 is 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 find the spare in a salvage shop or a parts store. replacement key for audi a4 is simple to test them - just switch your DMM into resistance mode and determine 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 in our 20vt turbo (3B AAN ABY) engines must be aware of the speed and position of the crankshaft in order to make a decision about timing of fuel injectors, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these sensors, the diagnostic scanner will display the codes that could trigger an engine shut down.
Some of the signs of a failed G28 sensor include an inaccurate gearbox rev counter the gears are shifting faster than normal, and/or a misfire when in gear. If you are experiencing any of these problems, it is likely that your sensor is failing and should be replaced. The good thing is that they are quite affordable and easily accessible particularly in the case of an 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 sensor could cause a myriad of issues in your car. It's a vital component of your Audi's transmission, because it communicates to the ECU about how fast or slow the car's crankshaft is turning. If the sensor fails, it could disrupt the performance of the transmission as well as the rest of the car's components.
The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It sends signals via an uncolored wire to the ECU pin T55/49. The ECU uses this signal to regulate fuel and boost, and also to timigrate. It also transmits 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. Also, you can 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. You should detect a resistance of approximately 1000 ohms in these areas. This is a typical component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.