How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located near the edges of the transmission just above the flywheel ring gear. It transmits a signal to the ECU via the grey wire T55/49 and then to the tachometer on the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated on the edge of transmission, directly above the flywheel ring. This sensor sends signals through the grey wire to pin T55/49. The ECU then uses this information to control the boost, fuel, and timig. It also sends signals to the G5 tachometer inside the instrument cluster.
The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft has reached TDC and also where the camshaft lies in order to activate the spark and injectors.
If this sensor fails when it fails, the ECU will display a P00160 error code. This indicates that the Crank Shaft is not in sync with the Intake Camshaft. It could also be a sign of an issue with the chain or a jump in the chain link of the upper chain of timing. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).
Testing is a bit challenging as there are two different pins for the connector and they serve different purposes however the best method to test it is by measuring resistance between the sensor and the ECU. When the sensor is operational, it should be reading approximately 1000 ohms. Examine for signs of coolant or oil in the connector bay if you have issues with this part.
2. Injectors
Yesterday accelerating full speed from highway paytoll i had an abrupt drop in power like the engine is out of gas or the injectors are not firing at all. Today, i pulled out the spark plugs, 3 were soaked with gazoline and the fourth was dry. When I start the engine with no sparks, I put a piece of tissue on top of each injector hole and the 3 that were drenched in gazoline jump out but the 4th stays shut. I tested the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. I think the issue is elsewhere.
I also tried to reset the PID but with no luck. The car is able to start if the G28 is unplugged and it runs perfectly when it is connected however it is experiencing intermittent misfires at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of -49c, even if I unplug it. I also noticed that the oil pressure gauge in the cockpit shows 2 bar while the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do, i think i've pretty much eliminated everything else. However, i'm afraid that i might have missed something. If anyone has any ideas please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals from the RPM sensor. The GM-style transmitter is identical to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily find a spare in a wrecking shop or parts store. audi a1 car key is simple to test them - just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They must be infinite ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that needs to know the position and speed of the crankshaft to make decisions about timing of the fuel injector, for example. In order to do this it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go bad you will get codes on the diagnostic scanner which can lead to engine shutdown.
A malfunctioning G28 sensor can cause an inaccurate speed counter for your gearbox, a gearbox that shifts more quickly than normal, and/or an unfire when in gear. If you are experiencing any of these problems, it is likely that your sensor is going bad and should be replaced. The good news is they are very affordable and readily available, especially when you're looking at the Bosch unit like ours. Alternatively, GM's version of this part would be a good option.
5. Tachometer
A failing engine sensor could cause a myriad of issues in your vehicle. It's an essential component of the Audi's transmission as it sends information to the ECU about how fast or slow the car's crankshaft is turning. If this sensor fails, it can affect the performance of the transmission and the other car's components.
The G5 engine speed sensor is located on the edge of the transmission, above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU then uses and processes the signal to control fuel, timig and boost and then transmitting it to the G5 tachometer inside the instrument cluster. You can determine if the sensor is in failure by examining the continuity of the sensor to the tachometer. Additionally, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 and pin T26a/12. It should show approximately 1000 ohms of resistance between those two pins. This is a typical component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU. Good ones might be availble in wrecking yards.