"Ask Me Anything": Ten Responses To Your Questions About Audi G28
How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. This sensor is located at the top of the transmission just above the flywheel ring gear. It transmits a signal to the ECU through the grey wire T55/49 and then to the tachometer on 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 an electrical signal to ECU pin T55/49 using the grey wire. The ECU utilizes this information to regulate the amount of fuel and boost. It also sends an indication to the G5 tachometer inside the instrument cluster.
The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft has reached TDC and also the position of the camshaft, in order to activate the spark and injectors.
If this sensor fails when it fails, the ECU will display an error code P00160. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of a chain stretch or a jumpy chain link in the upper chain of timing. The code will not appear without the additional information provided by other sensors (G4 or G40).
Testing can be a bit difficult as there are two different connector pins and they perform different functions but the best method to test it is to measure resistance between the sensor and the ECU. It should read about 1000 ohms if the sensor is in full operation. Look for signs of coolant, or oil in the connector bay if you have problems with this part.
2. Injectors
Yesterday, while accelerating from the highway paytoll at a high speed I noticed a significant drop in power. It was as if the engine was running out of gas. Or my injectors weren't firing. In the morning, i removed the spark plugs. Three were drenched in gazoline, the 4th one was dry. When I crank the engine, there are no sparks, i place a tissue on the top of each of the injector holes and the 3 drenched with gazoline jump out but the 4th stay shut. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 i get zero Ohm. So i assume the problem is elsewhere.
I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it runs fine with the G28 connected. However, the intermittent misfire problem still occurs at higher RPM. The coolant sensor (G62) even when it is unplugged, shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is zero.
I'm not sure what to do. I feel like i've pretty much eliminated everything else. I'm afraid i may have missed something. If anyone has any ideas please chime in! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal by 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 by putting your DMM in resistance mode and measure between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black end of the connector). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines requires to be aware of the position and speed of the crankshaft to determine timing of the fuel injector, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these go badly, you will see codes on the diagnostic scanner that can lead to engine shutdown.
Some of the symptoms of a failed G28 sensor are an inaccurate rev counter for the gearbox, gears shifting quicker than normal and/or misfiring when in gear. If you experience any of these problems, it is most likely that your sensor is deteriorating and requires replacement. They're inexpensive and easy to locate especially when they're an Bosch unit like ours. You can also choose the GM version of this part is also a great option.
5. Tachometer
A failing engine speed sensor could be the reason behind numerous problems in your vehicle. It is an important part of the transmission of your Audi since it sends information to the ECU about how fast or slowly the car's engine is turning. If how do i get a replacement key for my audi fails, it could affect the performance of the transmission, as well as the other car's components.
The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It transmits a signal via gray wire to ECU pin T55/49. The ECU then processes the signal to control fuel, timig, and boost, and also transmitting it to the G5 tachometer inside the instrument cluster. You can determine if the sensor is in failure by examining the continuity of the sensor to the tachometer. You can also check continuity between pin 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. You should detect the resistance to be around 1000 ohms between these points. This is a standard part that is found across the Audi 80, 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best ones could be available in wrecking yards.