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How to Replace an Audi G28 Engine Speed Sensor
In this video, Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. This sensor is situated near the transmission's edge over the flywheel gear. It transmits a signal the ECU via the grey wire (T55/49) which is then sent to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated at the edges of the transmission, just above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU utilizes this information to control fuel and boost. It also sends a signal 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 needs to know when the crankshaft is TDC and the location of the camshaft so it can trigger spark and injectors according to the situation.
If this sensor fails, the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync, possibly indicating the chain stretching or a jump link on the upper chain of timing. 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 various pins on the connector, and each has its own 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 read around 1000 ohms. Examine for evidence of coolant or oil in the connector bay if you are experiencing problems with this part.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at full speed I noticed a significant drop in power. It was like the engine had run out of gas. Or, my injectors weren't firing. In the morning, i removed the spark plugs, three were soaked with gazoline and the 4th one was dry. When i crank the engine without sparks, i place a tissue on top of each injector hole and the 3 drenched with gazoline pop out, but the 4th stays closed. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. i get zero ohm. I think the issue is in another location.
I also tried to reset the PID without success. The car will start if the G28 is disconnected and runs fine when it is connected but it still is experiencing intermittent misfires at higher RPM. audi advanced key (G62) shows the wrong temp value that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is zero.
I'm not certain what to do, i believe that i've ruled out everything else. I'm afraid i may have missed something. If anyone has any ideas please share them! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal sent by the RPM sensor. The GM-style sender is the same as the G4 and both are used in the 80, 100 200, UrS and RS2 cars so you can easily find one at a wrecking yard or from a parts store. It is simple to test them: simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector's end facing up). They should be infinite ohms.
4. audi advanced key of our 20vt turbo (3B AAN ABY) engines must know both the position and speed 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 of these sensors, the diagnostic scanner will show codes that could lead to an engine shut down.
The signs of a failed G28 sensor include an inaccurate gearbox rev counter, gears shifting quicker than normal, and/or a misfire when in gear. If you are experiencing any of these issues, it is most likely that your sensor is deteriorating and needs replacing. The good news is that they are very cheap and easy to find particularly when you're looking at a Bosch unit which is what ours are. Alternately, GM's version this part would be an excellent choice.
5. Tachometer
A faulty engine speed sensor could be a cause for numerous problems in your vehicle. It's a crucial component of the transmission of your Audi, as it transmits information to the ECU regarding how fast or slow the engine is spinning. This sensor can cause the transmission to malfunction and other car components to be affected.
The G5 engine speed sensor is located at the outside of the transmission above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 via a grey wire. The ECU utilizes this signal to regulate the flow of fuel and boost and also to timigrate. It also sends 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. Additionally, you can 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 see a resistance of approximately 1000 ohms in these areas. This is a common part across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU, so the best ones might be availble in wrecking yards.