How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is located near the edges of the transmission just above the flywheel ring 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
It is located on the outside of the transmission, above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through the grey wire. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends signals to the G5 tachometer in the instrument cluster.
The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can trigger spark and injectors according to the situation.
If this sensor fails the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync, possibly indicating the chain is stretched or a jump link on the upper chain of timing. However, the code won't be displayed on its own without additional information from other sensors (G4 and G40).
It's a bit tricky to test because there are various pins on the connector and they all have different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. If the sensor is operational, it should be reading around 1000 ohms. If you're experiencing issues with this part, check
replacement key for audi signs of coolant or oil in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at maximum speed I noticed a significant reduction in power. It was as if the engine had run out of gas. Or my injectors weren't firing. In the morning, i removed the spark plugs, three were drenched in gazoline, the fourth was dry. When I crank the engine, there are no sparks, i place a tissue on top of each injector hole, the 3 drenched with gazoline pop out, but the 4th stays closed. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found zero ohm. I'm assuming that the issue is in another location.
I also tried to reset the PID without success. The car will start if the G28 is not plugged in and runs fine when it is connected but it still has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows an ice temperature of -49c. Also, i noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.
I'm not sure what to do. I think I've ruled everything else out. I'm concerned that i may have missed something. Please let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal by the RPM sensor. The GM-style transmitter 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 junkyard or at a 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 upwards). They must be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY) engines must be aware of the speed and position of the crankshaft to make decisions regarding fuel injector timing, 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 cause the engine to shut down.
The signs of a failed G28 sensor are an inaccurate rev counter in the gearbox, gears shifting quicker than normal and/or misfiring when in gear. If you are experiencing any of these problems, it is likely your sensor is deteriorating and needs replacing. The good thing is that they are quite affordable and easy to find, especially in the case of the Bosch model, which is what ours are. Alternately, GM's version this part would be an excellent choice.
5. Tachometer
A damaged engine sensor could cause a myriad of issues in your vehicle. It's a vital component of your Audi's transmission, as it sends information to the ECU about how fast or slow the car's crankshaft is turning. This sensor can cause the transmission to malfunction and other components in the car to be affected.
The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It transmits signals via an uncolored wire to the ECU pin T55/49. The ECU then processes the signal to control the flow of fuel, timig and boost, and also sends it on to the G5 Tachometer located in the instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. There should be an average resistance of 1000 ohms between these points. This is the same across the
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Read the Full Post) 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS An and 1995 RS2 DU So, you may find good ones in wrecking yards.
