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 situated on the edge of the transmission, above the flywheel ring gear. It transmits 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 transmits a signal via the grey wire to pin T55/49. The ECU then uses this information to control fuel, timig and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.
The sensor is used to link with the G40 Camshaft position Sensor. The ecu has to be aware of when the crankshaft has reached TDC, and where the camshaft lies so that it can activate the spark and injectors.
If this sensor fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is not in sync with the Intake Camshaft. It could also be a sign of a chain stretch or a jumped chain link in the upper chain of timing. The code won't show without the additional information supplied by other sensors (G4 or G40).
Testing is a bit challenging because there are two connector pins and they perform different functions but the most effective way to test it is to measure resistance between the sensor and the ECU. If the sensor is functional, it should read around 1000 ohms. Look for signs of coolant or oil in the connector bay if you have problems with this part.
2. Injectors
Yesterday accelerating full speed from highway paytoll i had a big cut in power as if the engine was running out of gas or the injectors aren't firing anymore. I took out the spark plugs this morning, 3 were soaked in gasoline, and the 4th was dry. When I start the engine, there are no sparks, I put a piece of tissue on the top of each hole in the injector, the 3 drenched with gazoline leap out, however the 4th stay closed. I checked the ground connection on ECU pins 14/55,30/55 and 48/55 I got zero ohm. I'm assuming the issue is elsewhere.
I also tried to reset the PID without success. The car will start when the G28 is disconnected, but it is running fine with the G28 connected. However, the intermittent misfire problem still occurs at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is zero.
I'm not sure what to do, but i believe that i've ruled out everything else. But i'm worried that i might have missed something. Let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal sent by the RPM sensor. The GM-style transmitter is the same as the G4 and both function in the 80, 100 200, UrS and RS2 cars so you can easily find one at a junkyard or in a local parts store. Test them out - put 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 end). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines requires to be aware of the position and speed the crankshaft to make decisions regarding timing of the fuel injector, etc. It makes use of 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 shutdown.
Some of the signs of a failing G28 sensor include an inaccurate rev counter for the gearbox, gears shifting quicker than normal and/or a misfire when you're in gear. If you have any of these problems, it is likely your sensor is deteriorating and should be replaced. They're inexpensive and easy to locate particularly if they're an Bosch model like ours. You can also choose the GM version of this part is also a good option.
5. Tachometer
A failing engine speed sensor could be the reason behind a slew of issues in your vehicle. It's an essential component of the Audi's transmission because it communicates to the ECU about how fast or slow the car's crankshaft is rotating. If this sensor fails, it will cause problems for the transmission, as well as the other car's components.
The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It transmits an electrical signal through a gray wire to the ECU pin T55/49. audi spare keys is then able to process the signal to control fuel, timig, and boost as well as sends it on to the G5 Tachometer located in the instrument cluster. You can test the sensor for any failure by checking the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. There should be a resistance of approximately 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, so you might find them in wrecking yards.