How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. This sensor is located at the top of the transmission above the flywheel ring gear. It transmits a signal to the ECU via a grey wire (T55/49), then to the tachometer within the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the outside of the transmission, above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then uses this information to control the boost, fuel, and timig. It also sends a signal to the G5 Tachometer located in the instrument cluster.
The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu has 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 to function, the ECU will display a P00160 error message. This indicates that the Crank Shaft is not in alignment with the Intake Camshaft. It could also indicate a chain stretch or a jumped chain link in the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40).
Testing is a bit challenging because there are two connector pins and they serve different purposes but the most effective method to test it is by measuring resistance between the sensor and the ECU. When the sensor is functional, it should read about 1000 ohms. Examine for signs of coolant, or oil in the connector bay if you have issues with this component.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at maximum speed I noticed a massive reduction in power. It was like the engine had run out of gas. Or, my injectors were not firing. Today, i pulled out the spark plugs, three were drenched in gazoline, the fourth was dry. When i crank the engine without sparks i put tissue on the top of each hole in the injector, the 3 drenched with gazoline leap out, however the 4th stays closed. I checked the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. So i assume the problem is somewhere else.
I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it is running fine with the G28 audi key replacement connected. However, the intermittent misfire problem continues to occur at higher RPM. The coolant sensor (G62), even when unplugged, still shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows get more info 2 bar but the actual pressure is 0.
I don't know what to do. I believe that I've eliminated everything else. I'm worried that i might have missed something. If anyone has suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal 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 so you can easily find one at a salvage yard or at a parts store. Test them out to do - just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's side up) and 2 (2nd from read more left on the black connector's end). They must be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines must know both the position and speed of the crankshaft to determine timing of the fuel injector, etc. In order to do this it makes use of a Crank Position website Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues 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 gearbox rev counter, gears shifting quicker than normal and/or misfiring when in gear. If you experience any of these issues it is likely that your sensor is going bad and should be replaced. They're cheap and easy to find especially in the case of an Bosch model like ours. If you prefer, GM's version of this component is an option.
5. Tachometer
A faulty engine speed sensor could be a cause for a slew of issues in your car. It's an essential component of the transmission in your Audi because it relays information to the ECU about how fast or slow the car's engine is turning. If this sensor fails, it will disrupt the performance of the transmission as well as the other car's components.
The G5 engine speed sensor is located on the outside of the transmission above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 via a grey wire. The ECU uses this signal to regulate fuel and boost, and also to timigrate. It also sends it to the G5 Tachometer located in the instrument cluster. You can test the sensor for failure by checking continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) and between pin T6a/1 and the audi keys instrument cluster pin T26a/12. There should be a resistance of approximately 1000 ohms in these areas. This part is common 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 You may also find good ones in wrecking yards.