How to Replace an Audi G28 Engine Speed Sensor
In this video Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is located on the outside of the transmission just above the flywheel gear. It sends a message to the ECU via a grey wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The sensor is located at the edge of the transmission just above the flywheel ring gear the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 through a grey wire. The ECU uses this information to control fuel and boost. It also sends an alert to the G5 Tachometer in instrument cluster.
The sensor is used to correlate the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can activate spark and injectors accordingly.
If this sensor fails, the ECU will throw a P00160 code which means the Crank Shaft and Intake Camshaft are not in sync and possibly indicating chain stretch or a jumped link on the upper chain of timing. However the code will not appear on its own, without additional information from other sensors (G4 and G40).
Testing can be a bit difficult since there are two pins for the connector and they have different functions but the most effective method of testing it is by measuring resistance between the sensor and the ECU. When the sensor is functional, it should read around 1000 ohms. Examine for evidence of coolant or oil in the connector bay if you have issues with this component.
2. Injectors
Yesterday, when accelerating from highway paytoll at full speed I noticed a significant reduction in power. It was like the engine was running out of gas. Or my injectors weren't firing. Today, i pulled out the spark plugs. Three were drenched with gazoline the 4th one was dry. When I start the engine with no sparks i put tissue on top of each injector hole and the 3 that were drenched in gazoline pop out, but the 4th stays shut. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 i get 0ohm. Therefore, i think the issue is in another place.
I also tried to reset PID without success. The car can start if the G28 is disconnected and is running fine when it is connected however it is experiencing intermittent misfires at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is zero.
I'm not sure what to do. I feel like i've pretty much ruled everything else out. I'm afraid i may have missed something. If anyone has suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter 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 from a parts store. Testing them is easy 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 the left on the black end of the connector). They should be infinite Ohms.
4. click here in our 20vt turbo (3B AAN ABY) engines requires to know the position and speed of the crankshaft to determine timing of the fuel injector, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these go bad you will get codes on the diagnostic scanner that can lead to engine shutdown.
A damaged G28 sensor could result in an inaccurate gearbox speed counter and a gearbox which shifts faster than normal, or a misfire in gear. It is probable that the sensor is failing and requires to be replaced if you notice any of these symptoms. The good news is that they are very cheap and readily available, especially if you're looking at an Bosch model, like ours. You can also choose the GM version of this part is also a great option.
5. Tachometer
A damaged engine sensor could cause a number of problems in your car. It is a crucial part of your Audi's transmission, because it communicates to the ECU about how fast or slow the vehicle's crankshaft is spinning. If this sensor fails, it will disrupt the performance of the transmission as well as 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 and transmits a signal to the ECU at pin T55/49 via a grey wire. The ECU uses this signal to control the flow of fuel and boost and also timig. It also sends it to the G5 Tachometer located in the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. It should show around 1000 ohms of resistance between those two pins. This is a typical part across the Audi 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best ones might be availble in wrecking yards.