How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is situated on the edge of the transmission, above the flywheel ring gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the outside of the transmission, directly above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU utilizes this information to control boost and fuel. It also sends an indicator to the G5 Tachometer located in the instrument cluster.
The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can start spark and injectors accordingly.
If this sensor fails when it fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is out of sync with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jump in the chain link of the upper chain of timing. The code won't show without the additional information supplied by other sensors (G4 or G40).
Testing is a bit challenging since there are two connector pins, and they serve different purposes but the most effective method of testing it is to measure the resistance between the sensor and the ECU. If the sensor is functional, it should read about 1000 ohms. If you are having problems with this sensor, look for evidence of oil or coolant in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at a high speed I noticed a significant decrease in power. It was as if the engine had run out of gas. Or, my injectors weren't 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 and the 3 drenched with gazoline jump out but the 4th stay closed. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found zero ohm. Therefore, i think the issue is in another place.
I also tried to reset the PID without success. The car is able to start when the G28 is disconnected and it runs perfectly when check here it is plugged in but it still is experiencing intermittent misfires at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature of -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is 0.
I don't know what to do. I feel like i've pretty much all other possibilities out. I'm worried that i might have missed something. Please let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump in the g28 receives 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 which is why you can easily locate one at a wrecking yard or from a parts store. Testing them is easy - more info put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black connector's end). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that needs to know the speed and position of the crankshaft in order to make decisions about fuel injector timing etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you encounter a problem with either of these sensors, the diagnostic scanner will display the codes that could trigger an engine shutdown.
A failing G28 sensor could result in an inaccurate speed counter for your here gearbox, a gearbox that shifts faster than normal, and/or an unfire when in the gear. If you have any of these issues it is likely that your sensor is failing and requires replacement. The good thing is that they are very affordable and readily available particularly in the case of a Bosch unit which is more info what ours are. Alternatively, the GM version of this unit is also a good option.
5. Tachometer
A failing engine sensor could cause a myriad of issues in your vehicle. It is a crucial part of the Audi's transmission because it communicates to the ECU about how the car's crankshaft is turning. This sensor can cause the transmission to fail and other car components to be affected.
The G5 engine speed sensor is located at how much is a replacement audi key the edge of the transmission just above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 via an uncolored 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 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 detect a resistance of approximately 1000 ohms between these points. This is a standard part that is found across the Audi 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.