How to Replace an Audi G28 Engine Speed Sensor
In this video, Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. This sensor is situated at the edge of transmission over the flywheel gear. It transmits a signal to the ECU via an uncolored wire T55/49, then to the tachometer located on 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 an electrical signal to ECU pin T55/49 through a grey wire. The ECU then utilizes this information to regulate 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 must be aware when the crankshaft is TDC and where the camshaft is located so that it can activate spark and injectors accordingly.
If this sensor fails the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync and could indicate the chain stretching or a jump 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 is a bit tricky since there are two connector pins, and they perform different functions but the most effective method of testing it is by measuring resistance between the sensor and the ECU. It should read approximately 1000 ohms when the sensor is operating at its maximum. Look for signs of coolant or oil in the connector bay if you are experiencing issues with this component.
2. Injectors
Yesterday, while accelerating from the highway paytoll at maximum speed, i noticed a huge drop in power. It was like the engine had run out of gas. Or my injectors were not firing. This morning i pull out the spark plugs, 3 were drenched in gazoline, the fourth one was dry. When i crank the engine with no sparks i put tissue on the top of each hole in the injector and the 3 that were drenched in gazoline leap out, however the 4th stays shut. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. I got zero ohm. I'm here assuming that the issue is in another location.
I also tried to reset the PID without success. The car can start if the G28 is unplugged and is running fine when it is connected, but still has intermittent misfire issues 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 when the actual pressure is zero.
I'm not sure what to do, i believe that i've eliminated everything else. But i am afraid I might have missed something. If anyone has suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals from the RPM sensor. The GM-style sender 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 at a parts store. Testing them is easy by putting your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's side). They should be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that must know the speed and position of the crankshaft in order to make decisions about timing of the fuel injector, for example. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go wrong, you will receive codes on the diagnostic scanner that could cause engine shut down.
Some of the symptoms of a malfunctioning G28 sensor include an inaccurate rev counter for the gearbox, gears shifting quicker than normal, and/or a misfire when you are in gear. If you experience any of these issues, it is likely your sensor is failing and check here requires replacement. The good news is they are very affordable and easily accessible, especially in the case of the Bosch sensor, which is what we have. Alternatively, GM's version of this part is an excellent choice.
5. Tachometer
A failing engine speed sensor could be the cause of a slew of problems in your vehicle. It's a vital component of the Audi's transmission since it relays information to the ECU about how the car's crankshaft is rotating. When this sensor fails, it will disrupt the performance of the transmission, as well as the rest of the car's components.
The G5 engine sensor is located at the edge of transmission, check here above the flywheel ring. It transmits a signal via gray wire to ECU pin T55/49. The ECU uses this signal to regulate the amount of fuel and boost, and also timig. It also get more info relays it to the G5 Tachometer located in the instrument cluster. You can test for sensor failure by examining the continuity from the sensor to the tachometer. Additionally, you can examine the continuity between pins T55/49 of the click here ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 and pin T26a/12. You should detect the resistance to be around 1000 ohms between these points. This part is common across the Audi 80-100-200-RS2 range, beginning with the 1985 MC and up to the 1997 UrS AN and 1995 RS2 DU You may also find some good ones in wrecking yards.