Three Of The Biggest Catastrophes In Audi G28 History
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 near the edges of the transmission, above the flywheel ring gear. It transmits a signal to the ECU via an uncolored wire (T55/49), then to the tachometer within the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the outside of the transmission, just 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 indicator to the G5 Tachometer located in the instrument cluster.
The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft has reached TDC, and the location of the camshaft to trigger the spark and injectors.
If this sensor fails the ECU will throw a P00160 code which means the Crank Shaft and Intake Camshaft are not in sync and possibly indicating the chain stretching or a jump link on the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40).
It is a little tricky to test because there are various pins on the connector, and each one has different functions. The best way to do it is to measure the resistance between the ECU and the sensor. If the sensor is functional, it should read about 1000 ohms. If you're experiencing issues with this part, check for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday accelerating full speed from highway paytoll i had an abrupt drop in power like the engine is running out of gas or the injectors aren't firing any more. I took out the spark plugs this morning, 3 were soaked in gasoline, and the 4th was dry. I placed a tissue over each injector hole, and when I start the engine with no sparks, the 3 that have gazoline pop right out. The 4th one stays closed. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. i get zero Ohm. I assume that the problem is somewhere else.
I also tried to reset PID but without success. The car can start when the G28 is not plugged in and is running fine when it is plugged in but it still has intermittent misfire issues 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 while the actual pressure is 0.
I'm not certain what to do, as i believe that i've completely ruled out all other possibilities. I'm afraid i may have missed something. Please let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style transmitter is identical to the G4 and both are used in the 80, 100 200, UrS and RS2 cars which is why you can easily locate one at a junkyard or in a local parts store. It is simple to test them - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's side). They should be infinite ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines needs to know the speed and position of the crankshaft to make decisions regarding timing of fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these sensors go bad you will get codes on the diagnostic scanner which can lead to engine shutdown.
A malfunctioning G28 sensor could result in an inaccurate speed counter for the gearbox, a gearbox that shifts faster than normal, and/or a misfire while in the gear. If you are experiencing any of these issues, it is likely that your sensor is deteriorating and should be replaced. The good thing is that they are very affordable and readily available, especially if you're looking at the Bosch unit which is what we have. Alternately, GM's version this part would be an option.
5. Tachometer
A damaged engine sensor could cause a number of problems in your car. It's a vital component of the Audi's transmission because it communicates to the ECU about how fast or slow the vehicle's crankshaft is turning. When this sensor fails, it can cause problems for the transmission and the other car's components.
The G5 engine speed sensor is situated on the edge of the transmission above the flywheel ring gear and transmits a signal to the ECU at pin T55/49, via a grey wire. Audi A1 keys thekeylab.co.uk to control fuel, timig and boost as well as transmitting it to the G5 tachometer inside the 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 [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should see approximately 1000 ohms resistance between those points. This part is common 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.