How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. This sensor is located near the transmission's edge just above the flywheel gear. It transmits a signal the ECU via an uncolored wire (T55/49) and then 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 signals to ECU pin T55/49 using an uncolored wire. The ECU utilizes this information to regulate fuel and boost. It also sends an indication to the G5 tachometer inside the instrument cluster.
The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft reached TDC, and where the camshaft lies in order to activate the spark and injectors.
If this sensor fails, the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync, possibly indicating the chain stretching or a jump link on the upper chain of timing. The code won't show without the additional information provided by other sensors (G4 or G40).
It can be a bit difficult to test because there are several connector pins, and each one has different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. When the sensor is operational, it should be reading around 1000 ohms. Look for evidence of coolant or oil in the connector bay if you have problems with this part.
2. Injectors
Yesterday, when i was accelerating to the fullest speed from highway paytoll i had massive power loss as if the engine was running out of gas or injectors are not firing anymore. In the morning, i removed the spark plugs, 3 were soaked with gazoline and the 4th one was dry. When i crank the engine with no sparks, i place a tissue on the top of each of the injector holes and the 3 that were drenched in gazoline leap out, however the 4th stay closed. I tried to test the ground connections of ECU pins 14,30, and 48/55. I found zero ohm. I'm assuming the issue is elsewhere.
I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it works fine when the G28 connected. However the intermittent misfire issue continues to occur at higher RPM. audi a3 replacement key (G62) shows the wrong temperature of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is 0.
I'm not sure what to do. I feel like i've pretty much eliminated everything else. I'm worried that i might have missed something. Let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style transmitter is identical to the G4 and both are used in the 80 100 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or in a local parts store. Test them out to do - just put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's end up) and 2 (2nd from the 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 fuel injector timing, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these goes badly, you will see codes on the diagnostic scanner that can cause the engine to shut down.
A damaged G28 sensor can cause an inaccurate gearbox speed counter or a gearbox that shifts faster than normal, and/or a misfire while in the gear. It is possible that the sensor is failing and needs to be replaced if you encounter any of these signs. They are cheap and easy-to-find particularly in the case of a Bosch unit like ours. You can also choose the GM version of this part is also a good option.
5. Tachometer
A malfunctioning engine speed sensor could be a cause for many problems in your car. It's an essential component of your Audi's transmission, as it sends information to the ECU about how fast or slow the car's crankshaft is spinning. If this sensor fails, it will disrupt the performance of the transmission and the rest of the car's components.
The G5 engine speed sensor is located on the edge of the transmission, above the flywheel ring gear. It sends a signal to the ECU at pin T55/49 via a grey wire. The ECU then processes this signal to regulate the flow of fuel, timig and boost and then sends it on to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. You can also check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 as well as pin T26a/12. You should see around 1000 ohms of resistance between these two points. This is a standard component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good ones could be available in wrecking yards.