"The Ultimate Cheat Sheet" On 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. The sensor is located at the edge of transmission, above the flywheel gear. It sends a signal to the ECU via the grey wire (T55/49) which is then sent to the tachometer in the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission above the flywheel ring gear, the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 through a grey wire. The ECU then uses this information to control fuel, timig and boost. It also sends an alert to the G5 Tachometer within the instrument cluster.
The sensor is used to link with the G40 Camshaft position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC, and the location of the camshaft to trigger the spark and injectors.
If this sensor fails the ECU will throw the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync and possibly indicating the chain stretching or a jump link on the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40).
It is a little tricky to test because there are several pins on the connector, and each one has different functions. audi car keys G28CarKeys to test it is by measuring the resistance between the ECU and the sensor. It should read about 1000 ohms when it is operating at its maximum. If you're experiencing issues with this sensor, look for signs of coolant or oil in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at maximum speed, i noticed a huge drop in power. It was as if the engine was running out of gas. Or, my injectors were not firing. I pulled out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was unclean. I put tissue over each injector hole, and when I start the engine without sparks, the 3 with gazoline jump out. The fourth one remains shut. I checked the ground connection of ECU pins 14,30, and 48/55. I got 0ohm. So i assume the problem is in another place.
I also tried to reset the PID without success. The car will start if the G28 is unplugged and is running fine when it is connected however it has the intermittent misfire issue at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is 0.
I'm not sure what to do. I feel like i've pretty much eliminated everything else. But i am afraid i might have missed something. If anyone has any suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style sensor 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 junkyard or in a local parts store. Test them out by putting your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's end). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines needs to know both the speed and position of the crankshaft in order to make a decision about timing of the fuel injector, etc. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes wrong, you will receive codes on the diagnostic scanner that could cause engine shut down.
Some of the symptoms of a failing G28 sensor include an inaccurate gearbox rev counter and gears that shift faster than normal and/or misfiring when you are in gear. If you are experiencing any of these issues, it is likely that your sensor is failing and needs replacing. The good thing is that they are quite affordable and readily available, especially when you're looking at a Bosch unit which is what ours are. You can also choose the GM version of this part is also a good option.
5. Tachometer
A failing engine speed sensor could be a cause for a slew of issues in your car. It is an important part of the transmission in your Audi, as it transmits information to the ECU on how fast or slowly the engine is spinning. This sensor could cause the transmission to malfunction and other components of the car to be affected.
The G5 engine sensor is located at the edge of the transmission, over the flywheel ring. It transmits 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 check for sensor failure by examining the continuity of the sensor to the tachometer. Additionally, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]) and between pin T6a/1 and pin T26a/12. You should see the resistance to be around 1000 ohms in these areas. This is a common feature across the Audi 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS AN and 1995 RS2 Du So, you may find some good ones in wrecking yards.