Audi G28: The Good, The Bad, And The Ugly
How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. The sensor is located near the transmission's edge over the flywheel gear. It sends a signal to the ECU via a grey wire (T55/49) which is then sent to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the outside of the transmission, above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU then uses this information to control the boost, fuel, and timig. It also sends an indication to the G5 Tachometer within the instrument cluster.
The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft has reached TDC and also the position of the camshaft, to trigger the spark and injectors.
If this sensor fails, the ECU will display an error code P00160. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of a chain stretch or a jumped chain link in the upper chain of timing. However, the error code won't appear on its own without additional information from other sensors (G4 and G40).
It's a bit tricky to test since there are several pins on the connector and each has its own functions. The best way to do it is to measure the resistance between the ECU and the sensor. If the sensor is operational, it should read around 1000 ohms. If you're experiencing issues with this part, check for signs of coolant or oil in the connector bay.
2. Injectors
Yesterday, when i was accelerating to the fullest speed from highway paytoll, I experienced massive power loss as if the engine was running out of gas or injectors aren't firing any more. I pulled out the spark plugs this morning and found that 3 were soaked in gasoline, and the 4th was dry. When i crank the engine, there are no sparks, I put a piece of tissue on top of each injector hole and the 3 drenched with gazoline pop out, but the 4th stay closed. I tried to test the ground connections of ECU pins 14,30 and 48/55. I got zero ohm. audi advanced key think the issue is somewhere else.
I also tried to reset the PID without success. The car will start when the G28 is unplugged and runs fine when it is plugged in but it still has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even when it is unplugged, shows temperatures of -49c. audi a5 replacement key noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is zero.
I'm not sure what to do. I believe that I've all other possibilities out. However, i'm afraid that i might have missed something. If anyone has any ideas please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style transmitter is similar to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. It is easy to find a spare in a wrecking shop or parts store. Test them out by putting your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's side). They must be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines must know the position and speed of the crankshaft in order to make a decision about timing of the fuel injector, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either one of these, the diagnostic scanner will show the codes that could trigger the engine shutting down.
A malfunctioning G28 sensor can cause an inaccurate gearbox speed counter and a gearbox which shifts faster than normal, and/or an unfire when in the gear. It is possible that your sensor is failing and requires to be replaced if you encounter any of these signs. The good thing is that they are quite affordable and easily accessible particularly in the case of a Bosch model, which is what we have. You can also choose the GM version of this unit is also a good option.
5. Tachometer
A damaged engine sensor could cause a myriad of issues within your vehicle. It's a vital component of your Audi's transmission, because it communicates to the ECU about how the car's crankshaft is rotating. When this sensor fails, it can affect the performance of the transmission and the other car's components.
The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It transmits signals via gray wire to ECU pin T55/49. The ECU then processes this signal to control fuel, timig, and boost and then sends it on to the G5 tachometer inside the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. There should be the resistance to be around 1000 ohms between these two points. This is a common part 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.