The Most Pervasive Issues In Audi G28
How to Replace an Audi G28 Engine Speed Sensor
In this video Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is located at the top of the transmission, above the flywheel ring gear. It sends a message to the ECU via the grey wire T55/49 and then to the tachometer on the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated at the edges of the transmission, just above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU uses this information to control the amount of fuel and boost. It also sends an indicator to the G5 Tachometer within the instrument cluster.
The sensor is used to correlate 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 according to the situation.
If this sensor fails, the ECU will display an error code P00160. This means that the Crank Shaft is not in sync with the Intake Camshaft. It could also be a sign of an issue with the chain or a jump in the chain link of the upper chain. The code won't appear without the additional information provided by other sensors (G4 or G40).
It is a little tricky to test since there are various pins on the connector, and each one has different functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. It should read around 1000 ohms if the sensor is operating at its maximum. If you are having problems with this part, check for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at full speed I noticed a massive decrease in power. It was like the engine had run out of gas. Or, my injectors were not firing. I took out the spark plugs this morning, three were soaked with gasoline and the fourth was unclean. When audi key replacement crank the engine without sparks, I put a piece of tissue on the top of each of the injector holes, the 3 drenched with gazoline leap out, however the 4th stays shut. I tested the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got zero ohm. I think the issue is in another location.
I also tried to reset PID but without success. The car will start when the G28 is unplugged, and it works fine when the G28 plugged in. However, the intermittent misfire problem continues to occur at higher RPM. The coolant sensor (G62) even when unplugged, still shows temperatures 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 don't know what to do. I believe that I've eliminated everything else. But i am afraid I may have missed something. Let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter is the same as the G4 and they both work in the 80 100, 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or from a parts store. It is simple to test them - just put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must be infinite ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY) engines requires to know the position and speed the crankshaft in order to make a decision about timing of fuel injectors, etc. In order to do this it makes use of 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 the codes that could trigger the engine shutting down.
The signs of a failing G28 sensor include an inaccurate rev counter for the gearbox, gears shifting quicker than normal, and/or a misfire when in gear. If you have any of these problems, it is likely that your sensor is going bad and should be replaced. They're cheap and easy to find particularly in the case of an Bosch model like ours. Alternately, GM's version this part would be an option.
5. Tachometer
A failing engine speed sensor could be the cause of many issues in your vehicle. It is an important part of the transmission of your Audi since it sends information to the ECU regarding how fast or slow the car's engine is spinning. When this sensor fails, it will affect the performance of the transmission and the rest of the car's components.
The G5 engine speed sensor is located on the outside of the transmission just above the flywheel ring gear. It sends a signal to the ECU at pin T55/49, via an uncolored wire. The ECU then processes this signal to regulate fuel, timig, and boost as well as transmitting it to the G5 tachometer inside the instrument cluster. You can test for sensor failure by examining the continuity of the sensor to the tachometer. Also, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 as well as pin T26a/12. It should show around 1000 ohms of resistance between these two points. This is a common 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.