The 10 Most Terrifying Things About Audi G28
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. This sensor is situated at the edge of transmission, above the flywheel gear. It sends a message to the ECU through an uncolored wire T55/49, then to the tachometer on the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission above the flywheel ring gear the G28 Engine Speed Sensor sends signals to ECU pin T55/49 via an uncolored wire. The ECU utilizes this information to control the amount of fuel and boost. It also sends an alert 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 has to know when the crankshaft has reached TDC and also where the camshaft lies in order to activate the spark and injectors.
If this sensor fails, the ECU will display a P00160 error code. This means that the Crank Shaft is out of alignment with the Intake Camshaft. It could also be a sign of an issue with the chain or a jumped chain link in the upper chain. However the code will not appear on its own, without additional information from other sensors (G4 and G40).
It's a bit tricky to test since there are several pins on the connector and each one has different functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. If the sensor is operational, it should be reading about 1000 ohms. Check for evidence of coolant or oil in the connector bay if there are issues with this part.
2. Injectors
Yesterday accelerating full speed from highway paytoll i had a big cut in power like the engine is out of gas or injectors are not firing at all. In the morning, i removed the spark plugs, three were soaked with gazoline and the fourth was dry. When I start the engine with no sparks, I put a piece of tissue on top of each injector hole and the 3 that were drenched in gazoline jump out but the 4th stays closed. I tested the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got zero ohm. I'm assuming that the issue is in another location.
I also tried to reset the PID with no success. The car will start when the G28 is unplugged, and it is running fine with the G28 plugged in. However, the intermittent misfire problem continues to occur 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 0.
I'm not sure what to do. I believe that I've all other possibilities out. But i am afraid i might have missed something. If anyone has any suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal sent by 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 so you can easily find one at a wrecking yard or from a parts store. Testing them is easy to do - just 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 end of the connector). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines are equipped with an ECU that must be aware of the speed and position of the crankshaft to make a decision about fuel injector timing etc. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If The Key Lab encounter a problem with either one of these, the diagnostic scanner will display codes that could lead to an engine shutdown.
A malfunctioning G28 sensor could cause an inaccurate speed counter for your gearbox, a gearbox that shifts faster than normal, and/or a misfire while in gear. It is possible that your sensor is failing and requires to be replaced if you experience any of these symptoms. They're inexpensive and easy to locate especially if they're an Bosch model like ours. Alternately, the GM version of this unit is also a good option.
5. Tachometer
A malfunctioning engine speed sensor could be a cause for numerous issues with your car. 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. This sensor can cause the transmission to fail and other components in the car to be affected.
The G5 engine speed sensor is situated on the outside of the transmission above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 through a grey wire. The ECU is then able to process this signal to regulate the flow of fuel, timig and boost as well as transmitting it to the G5 tachometer in the instrument cluster. You can test for sensor failure by examining the continuity from the sensor to the tachometer. Also, you can check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]) and between pin T6a/1 and pin T26a/12. You should see an average resistance of 1000 ohms in these areas. This is the same across the Audi 80-100-200-RS2 range, from the 1985 MC all the way up to the 1997 UrS An and 1995 RS2 Du You may also find some good ones in wrecking yards.