How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. This sensor is located on the edge of the transmission above the flywheel ring gear. It transmits a signal the ECU via a grey wire (T55/49), then to the tachometer within 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 an electrical signal to ECU pin T55/49 using a grey wire. The ECU utilizes this information to regulate fuel and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.
The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft reached TDC and also the location of the camshaft so that it can activate the spark and injectors.
If this sensor fails, the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync and could indicate the chain stretching or a jump link on the upper chain of timing. The code will not appear without the additional information supplied by other sensors (G4 or G40).
It can be a bit difficult to test since there are various pins on the connector, and they all have different functions. The best way to do it is to measure the resistance between the ECU and the sensor. It should read about 1000 ohms when it is operating at its maximum. If you're experiencing issues with this sensor, look for evidence of coolant or oil in the connector bay.
2. i loved this , as i was accelerating off the highway paytoll at full speed, i noticed a huge decrease in power. It was as if the engine had run out of gas. Or my injectors were not firing. Today, i pulled out the spark plugs, 3 were drenched with gazoline the fourth was dry. When I crank the engine with no sparks, I put a piece of tissue on the top of each hole in the injector and the 3 that were drenched in gazoline pop out, but the 4th stays shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I got zero ohm. I assume that the problem is somewhere else.
I also tried to reset the PID but with no luck. The car will start when the G28 is disconnected, but it is running fine with the G28 plugged in. However the intermittent misfire issue persists at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is zero.
I'm not sure what to do. I believe that I've ruled everything else out. I'm worried that i might have missed something. Let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals from the RPM sensor. The GM-style sensor is identical to 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 junkyard or from a parts store. It is simple to test them - simply switch your DMM into resistance mode and test 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 have an ECU that has to know the speed and position of the crankshaft in order to make decisions about fuel injector timing etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either one of these, the diagnostic scanner will show codes that could lead to an engine shutdown.
A malfunctioning G28 sensor could result in an inaccurate gearbox speed counter or a gearbox that shifts more quickly than normal, and/or a misfire in gear. It is possible that your sensor is failing and requires to be replaced if you encounter any of these signs. The good news is they are quite affordable and readily available particularly if you're looking at the Bosch model, which is what ours are. Alternatively, GM's version of this part is an option.
5. Tachometer
A failing engine sensor could cause a variety of issues within your vehicle. It's a crucial component of the transmission of your Audi because it relays information to the ECU about how fast or slow the car's engine is turning. This sensor can cause the transmission to fail and other components in the car to be affected.
The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It sends a signal via gray wire to ECU pin T55/49. The ECU uses this signal to control the flow of fuel and boost and also to timigrate. It also transmits it to the G5 Tachometer in instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. It should show around 1000 ohms of resistance between these two points. This is a common 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. Good parts could be found in wrecking yards.