10 Quick Tips 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. The sensor is located on the edge of the transmission just above the flywheel ring gear. It transmits a signal the ECU via the grey wire (T55/49) and then to the tachometer located in 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 through an uncolored wire. The ECU utilizes this information to regulate fuel and boost. spare audi key sends an indication to the G5 tachometer in 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 the position of the camshaft, to trigger the spark and injectors.
If this sensor fails the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync, possibly indicating the chain stretching or a jump link on 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 as there are two different connector pins, and they serve different purposes but the most effective method to test it is to measure resistance between the sensor and the ECU. When the sensor is functional, it should read around 1000 ohms. Look for audi a1 keys of coolant, or oil in the connector bay if you have issues with this component.
2. Injectors
Yesterday, while accelerating from the highway paytoll at a high speed I noticed a massive decrease in power. It was like the engine was running out of gas. Or, my injectors were not firing. I took out the spark plugs this morning and found that 3 were soaked in gasoline, and the fourth was unclean. I put tissue over each injector hole, and when I start the engine without sparks, the ones that have gazoline pop right out. The 4th one remains closed. I checked the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. So i assume the problem is somewhere else.
I also tried to reset PID without success. The car will start when the G28 is disconnected, but it works fine when the G28 plugged in. However the intermittent misfire issue still occurs at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature of -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is zero.
I don't know what to do. I think I've eliminated everything else. I'm concerned that i may have missed something. Let me know If 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 sensor is identical to the G4 and both function in the 80 100 200, UrS and RS2 cars so you can easily find one at a salvage yard or in a local parts store. It is easy to test them - simply put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines requires to know the position and speed the crankshaft in order to make a decision about timing of the fuel injector, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these go bad you will get codes on the diagnostic scanner that could cause engine shut down.
A damaged G28 sensor can cause an inaccurate speed counter for your gearbox or 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 your sensor is deteriorating and should be replaced. The good news is they are quite affordable and easily accessible, especially if you're looking at an Bosch model, which is what ours are. Alternately, the GM version of this unit is also a good choice.
5. Tachometer
A damaged engine sensor could cause a myriad of issues in your vehicle. It is an important part of the transmission in your Audi, as it transmits information to the ECU regarding how fast or slow the engine is spinning. If the sensor fails, it could affect the performance of the transmission, as well as the rest of the car's components.
The G5 engine speed sensor is situated on the outside of the transmission above the flywheel ring gear and sends a signal to the ECU at pin T55/49, via an uncolored wire. The ECU utilizes this signal to regulate the flow of fuel and boost and also timig. It also sends it to the G5 Tachometer in instrument cluster. You can test for sensor failure by checking continuity from the sensor to the tachometer. You can also verify 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. It should show approximately 1000 ohms of resistance between those two pins. This is a standard part that is found across the Audi 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good ones could be available in wrecking yards.