The 10 Scariest Things About Audi G28
How to Replace an audi smart key replacement G28 Engine Speed Sensor
In this video, Charles the Humble Mechanic demonstrates 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 the ECU via an uncolored wire (T55/49) and then to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission, above the flywheel ring gear G28 Engine Speed Sensor sends signals to ECU pin T55/49 through an uncolored wire. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends a signal to the G5 tachometer inside the instrument cluster.
The sensor is used to link with the G40 Camshaft position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is so it can activate spark and injectors in the right way.
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 indicate an issue with the chain or a jumped chain link in the upper timing chain. However, the code won't be displayed on its own without additional information from other sensors (G4 and G40).
It is a little tricky to test since there are different connector pins, and they all have different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. It should read about 1000 ohms if the sensor is operating at its maximum. Look replacement key for audi signs of coolant, or oil in the connector bay if you are experiencing issues with this part.
2. Injectors
Yesterday, while accelerating at full speed from the highway paytoll i had an abrupt drop in power like the engine is out of gas or the injectors are not firing anymore. Today, i pulled out the spark plugs, 3 were drenched in gazoline, the fourth was dry. I placed a tissue over each hole in the injector and when i start the engine without sparks, the three with gazoline jump out. The 4th one remains closed. I tested the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I get zero Ohm. I think the issue is somewhere else.
I also tried to reset the PID but with no luck. The car is able to start when the G28 is disconnected and is running fine when it is connected, but still has intermittent misfire issues at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows temperatures of -49c. Also, i noticed that the oil pressure gauge in the cockpit shows 2 bar while the actual pressure is 0.0 when I crank up the engine.
I'm not sure what to do, but i feel i have pretty much eliminated everything else. But i am afraid I may have missed something. If anyone has suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style sender is identical to the G4 and both are used in the 80 100, 200, UrS and RS2 cars so you can easily find one at a junkyard or from a parts store. It is simple to test them - just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must 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. To accomplish this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either one of these, the diagnostic scanner will display codes that could cause an engine shutdown.
A failing G28 sensor can cause an inaccurate speed counter key for audi the gearbox and a gearbox which shifts faster than normal, and/or an unfire when in the gear. If you have any of these problems, it is most likely that your sensor is failing and should be replaced. They are cheap and easy-to-find particularly if they're an Bosch model like ours. Alternately, GM's version this component is a good option.
5. Tachometer
A failing engine sensor could cause a number of problems in your car. It's a vital component of your programming audi key's transmission, because it communicates to the ECU about how fast or slow the vehicle's crankshaft is turning. When this sensor fails, it could cause problems for the transmission and the rest of the car's components.
The G5 engine sensor is located near the edge of transmission, above the flywheel ring. It transmits signals via an uncolored wire to the ECU pin T55/49. The ECU is then able to process this signal to regulate the flow of fuel, timig and boost, and also sends it on to the G5 Tachometer located in the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. It should show approximately 1000 ohms of resistance between those points. This is a common part across the audi a4 replacement key 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best ones could be available in wrecking yards.