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. The sensor is located at the edge of transmission, above the flywheel gear. It transmits a signal the ECU via an uncolored wire (T55/49) which is then sent to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
The sensor is located at the edge of the transmission above the flywheel ring gear the G28 Engine Speed Sensor sends signals to ECU pin T55/49 using a grey wire. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends an indication to the G5 Tachometer located in the instrument cluster.
The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and the location of the camshaft so it can start spark and injectors in the right way.
If this sensor fails, the ECU will throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync and possibly indicating the chain is stretched or a jump link on the upper timing chain. The code will not appear without the additional information provided by other sensors (G4 or G40).
Testing is a bit challenging since there are two pins for the connector and they have different functions but the most effective method of testing it is to measure the resistance between the sensor and the ECU. It should read around 1000 ohms when it is in full operation. If you are having problems with this part, check for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, while accelerating at full speed from the highway paytoll, I experienced massive power loss like the engine is running out of gas or the injectors aren't firing any more. In the morning, i removed the spark plugs. Three were soaked with gazoline and the fourth one was dry. When I start the engine without sparks, i place a tissue on the top of each hole in the injector and the 3 drenched with gazoline pop out, but the 4th stays shut. I checked the ground connection on ECU pins 14/55,30/55 and 48/55 I get 0ohm. I think the issue is somewhere else.
I also tried to reset the PID but without success. The car is able to start if the G28 is not plugged in and runs fine when it is plugged in but it still has intermittent misfire issues at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature of -49c even when i unplug it. I also noticed that the oil pressure gauge in the cockpit shows 2 bar when the actual pressure is 0.0 when I crank up the engine.
I don't know what to do. I feel like i've pretty much all other possibilities out. But i am afraid i might have missed something. Please let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals from the RPM sensor. The GM-style transmitter is similar to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. replacement audi key is easy to find a spare in a wrecking shop or 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 end up) and 2 (2nd from left on the black connector's side). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines needs to be aware of the position and speed the crankshaft to determine timing of fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you have a problem with either one of these, the diagnostic scanner will display codes that could lead to the engine shutting down.
A malfunctioning G28 sensor could cause an inaccurate speed counter for the gearbox, a gearbox that shifts faster than normal, or a misfire in the gear. If you have any of these issues, it is likely that your sensor is deteriorating and requires replacement. The good news is that they are very affordable and easily accessible particularly in the case of a Bosch sensor, which is what ours are. You can also choose the GM version of this unit is also a good choice.
5. Tachometer
A malfunctioning engine speed sensor could be a cause for numerous issues with your vehicle. It's an essential component of your Audi's transmission, as it sends information to the ECU about how fast or slow the vehicle's crankshaft is spinning. When this sensor fails, it will cause problems for the transmission as well as the rest of the car's components.
The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It sends signals via a gray wire to the ECU pin T55/49. The ECU then uses and processes the signal to control fuel, timig and boost as well as sends it on 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. You can also examine the continuity between pins 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 see around 1000 ohms of resistance between those points. This is a common component across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.