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 over the flywheel gear. It transmits a signal to the ECU via the grey wire (T55/49) and then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission above the flywheel ring gear, the G28 Engine Speed Sensor sends signals to ECU pin T55/49 using an uncolored wire. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends an indication to the G5 tachometer in the instrument cluster.
The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can activate spark and injectors according to the situation.
If this sensor fails, the ECU will throw the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync and possibly indicating chain stretch or a jumped 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 because there are two connector pins and they serve different purposes however the best method to test it is by measuring resistance between the sensor and the ECU. If the sensor is functional, it should read approximately 1000 ohms. Examine for signs of coolant or oil in the connector bay if there are problems with this part.
2. Injectors
Yesterday, while accelerating from the highway paytoll at a high speed I noticed a massive reduction in power. It was as if the engine was running out of gas. Or my injectors were not firing. I took out the spark plugs this morning and found that 3 were soaked with gasoline and the fourth was unclean. I put a piece of tissue over each hole in the injector and when i start the engine without sparks, the three that have gazoline pop right out. The 4th one remains shut. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I get zero Ohm. genuine audi key replacement 'm assuming that the issue is elsewhere.
I also tried to reset PID but without success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However the intermittent misfire issue still occurs at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature value of -49c even when i unplug it. I also noticed that the gauge for oil pressure in the cockpit shows 2 bar, whereas the actual pressure is 0.0 if i crank up the engine.
I don't know what to do. I think I've eliminated everything else. I'm worried that i might have missed something. Let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal from the RPM sensor. The GM-style sensor is identical to the G4 and both function in the 80, 100 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or from a parts store. Testing them is easy by putting your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black connector's end). They must be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to be aware of the speed and position of the crankshaft to make decisions regarding 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 of these, the diagnostic scanner will display codes that could cause an engine shut down.
Some of the signs of a failed G28 sensor are an inaccurate rev counter in the gearbox, gears shifting quicker than normal and/or a misfire when in gear. It is likely that your sensor is failing and requires to be replaced if you encounter any of these signs. They are cheap and easy-to-find particularly in the case of an Bosch unit like ours. You can also choose the GM version of this part is also a good choice.
5. Tachometer
A failing engine sensor could cause a number of problems in your car. It is an important part of the transmission of your Audi because it relays information to the ECU on how fast or slow the engine is turning. If this sensor fails, it will cause problems for the transmission and the rest of the car's components.
The G5 engine speed sensor is located at the outside of the transmission above the flywheel ring gear. It sends a signal to the ECU at pin T55/49, via an uncolored wire. The ECU utilizes this signal to control the flow of fuel and boost and also to timigrate. It also sends it to the G5 Tachometer in instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, 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. You should observe around 1000 ohms of resistance between these two 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 the 1995 RS2 DU, so you might find good ones in wrecking yards.