How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. This sensor is situated near the transmission's edge, above the flywheel gear. It transmits a signal the ECU via an uncolored wire (T55/49) which is then sent to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends signals to ECU pin T55/49 through the grey wire. 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 is used to connect the G40 Camshaft position Sensor. The ecu must know when the crankshaft reached TDC and also the location of the camshaft to trigger the spark and injectors.
If this sensor fails, the ECU will display a P00160 error message. genuine audi key replacement uk indicates that the Crank Shaft is out of line with the Intake Camshaft. It could also indicate a chain stretch or a jump in the chain link of the upper chain. However, the code won't be displayed on its own without additional information from other sensors (G4 and G40).
Testing is a bit tricky because there are two pins for the connector and they perform different functions but the best way to test it is to measure the resistance between the sensor and the ECU. It should read approximately 1000 ohms when the sensor is operating at its maximum. If you're experiencing issues with this part, check for signs of coolant or oil in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at a high speed, i noticed a huge drop in power. It was like the engine was running out of gas. Or my injectors were not firing. Today, i pulled out the spark plugs, 3 were drenched with gazoline the fourth one was dry. I put a piece of tissue over each hole in the injector and when i start the engine with no sparks, the ones with gazoline jump out. The 4th one remains shut. I checked the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. I'm assuming that the issue is elsewhere.
I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it runs fine with the G28 connected. However the intermittent misfire issue still occurs at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature of -49c even when i unplug it. 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, but i feel i have pretty much ruled out everything else. I'm worried that i might have missed something. If anyone has any suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter is identical to 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 salvage yard or at a parts store. It is simple to test them by putting your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from the left on the black connector's side). They should be infinite ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY) engines must be aware of the position and speed the crankshaft in order to make a decision about fuel injector timing, etc. To accomplish 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 which could cause engine shut down.
The signs of a failed G28 sensor include an inaccurate rev counter for the gearbox and gears that shift faster than normal and/or misfiring when you are in gear. It is likely that your sensor is failing and needs to be replaced if you encounter any of these signs. The good thing is that they are quite affordable and easy to find particularly if you're looking at a Bosch sensor, which is what ours are. Alternatively, the GM version of this unit is also a good choice.
5. Tachometer
A damaged engine sensor could cause a variety of issues in your car. It's an essential component of your Audi's transmission, because it communicates to the ECU about how fast or slow the car's crankshaft is spinning. This sensor could cause the transmission to fail and other components in the car to be affected.
The G5 engine speed sensor is located at the outside of the transmission just above the flywheel ring gear. It sends a signal to the ECU at pin T55/49 through a grey wire. The ECU then processes the signal to control the flow of fuel, timig and boost and then transmitting it to the G5 tachometer inside the instrument cluster. You can determine if the sensor is in failure by checking continuity from 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 and pin T26a/12. You should detect 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.