How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches 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 sends a signal to the ECU via a grey wire (T55/49), then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated on the outside of the transmission, directly above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU uses this information to regulate the amount of fuel and boost. It also sends an alert to the G5 Tachometer within the instrument cluster.
The sensor is used to correlate the G40 Camshaft position Sensor. The ecu must know when the crankshaft reached TDC and also the position of the camshaft, in order to 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 are out of sync, possibly indicating the chain is stretched 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).
Testing can be a bit difficult because there are two pins for the connector and they serve different purposes but the best method to test it is by measuring resistance between the sensor and the ECU. When the sensor is operational, it should read approximately 1000 ohms. Examine for signs of coolant or oil in the connector bay if you have problems with this part.
2. Injectors
Yesterday, when accelerating from highway paytoll at a high speed I noticed a massive drop in power. It was as if the engine was running out of gas. Or my injectors weren't firing. I pulled out the spark plugs this morning, three were drenched in gasoline and the fourth was dry. TheKeyLab put a piece of tissue over each hole in the injector and when I start the engine without sparks, the ones that have gazoline pop right out. The fourth one remains closed. I tried to test the ground connections of ECU pins 14,30, and 48/55. I found zero ohm. I'm assuming the issue is somewhere else.
I also tried to reset the PID without success. The car is able to start when the G28 is not plugged in and it runs perfectly when it is plugged in but it still is experiencing intermittent misfires at higher RPM. The coolant sensor (G62), even when it is unplugged, shows temperatures of -49c. I also noticed that the oil pressure gauge in the cockpit shows 2 bar when the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do. I believe that I've ruled everything else out. However, i'm afraid that I might have missed something. Let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal by the RPM sensor. The GM-style sender is identical to the G4 and both are used in the 80 100 200, UrS and RS2 cars so you can easily find one at a wrecking yard or from a parts store. It is simple to test them - simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They should be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines must know both the position and speed of the crankshaft to make decisions regarding fuel injector timing, etc. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either of these, the diagnostic scanner will show the codes that could trigger an engine shutdown.
The signs of a failing G28 sensor include an inaccurate rev counter for the gearbox and gears that shift faster than normal and/or misfiring when you're in gear. It is probable that the sensor is failing and requires to be replaced if you notice any of these symptoms. They are cheap and easy-to-find especially in the case of an Bosch sensor like ours. You can also choose the GM version of this component is also a good option.
5. Tachometer
A damaged engine sensor could cause a myriad of issues within your vehicle. It's an essential component of the transmission in your Audi because it relays information to the ECU on how fast or slowly the engine is spinning. If the sensor fails, it can disrupt the performance of the transmission, as well as the rest of the car's components.
The G5 engine speed sensor is situated on the outside of the transmission above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 via an uncolored wire. The ECU utilizes this signal to regulate the amount of fuel and boost, and also timig. It also relays it to the G5 Tachometer in instrument cluster. You can determine if the sensor is in failure by examining the continuity from the sensor to the tachometer. Also, 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 as well as pin T26a/12. There should be a resistance of approximately 1000 ohms between these points. This is a common feature across the Audi 80-100-200-RS2 series, starting from the 1985 MC up to the 1997 UrS AN and 1995 RS2 Du So, you may find some good ones in wrecking yards.