How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. This sensor is situated near the transmission's edge over the flywheel gear. It sends a signal to the ECU via the grey wire (T55/49), then to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
The sensor is located at the edge of the transmission just 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 fuel, timig and boost. It also sends signals to the G5 tachometer in the instrument cluster.
The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and the location of the camshaft so it can start spark and injectors according to the situation.
If this sensor fails to function, the ECU will display a P00160 error code. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also indicate an issue with the chain or a jumpy chain link in the upper timing chain. However the code will not appear on its own without additional information from other sensors (G4 and G40).
Testing is a bit tricky since there are two connector pins, and they perform different functions but the best method to test it is by measuring resistance between the sensor and the ECU. If the sensor is operational, it should be reading about 1000 ohms. Examine for signs of coolant or oil in the connector bay if you are experiencing issues with this component.
2. Injectors
Yesterday, when accelerating from highway paytoll at full speed I noticed a massive drop in power. It was like the engine had run out of gas. Or my injectors were not firing. In the morning, i removed the spark plugs, 3 were soaked with gazoline and the fourth one was dry. When I crank the engine without sparks i put tissue on top of each injector hole, the 3 drenched with gazoline pop out, but the 4th one stays shut. I tested the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. I'm assuming the issue is elsewhere.
I also tried to reset the PID but without success. The car will start when the G28 is disconnected, but it is running fine with the G28 connected. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62), even when it is unplugged, shows a temperature of -49c. Also, i noticed that the gauge for oil pressure in the cockpit shows 2 bar, whereas the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do. I think I've ruled everything else out. I'm afraid i may have missed something. If anyone has any suggestions, please chime in! 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 similar to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily locate a spare in a wrecking shop or a parts store. It is easy to test them - just switch 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. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines must be aware of the position and speed the crankshaft to make decisions regarding fuel injector timing, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you have a problem with either one of these, the diagnostic scanner will display codes that could cause an engine shut down.
audi a1 key failing G28 sensor could cause an inaccurate speed counter for your gearbox, a gearbox that shifts faster than normal, or an unfire when in gear. If you have any of these problems, it is likely that your sensor is going bad and needs replacing. They are cheap and easy-to-find, especially in the case of an Bosch unit like ours. You can also choose the GM version of this part is also a good choice.
5. Tachometer
A damaged engine sensor could cause a myriad of issues in your vehicle. It's an essential component of the transmission of your Audi because it relays information to the ECU regarding how fast or slowly the car's engine is spinning. If the sensor fails, it will cause problems for the transmission, as well as the rest of the car's components.
The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It sends a signal via gray wire to ECU pin T55/49. The ECU uses this signal to regulate fuel and boost, and also to timigrate. It also sends it to the G5 Tachometer in instrument cluster. You can test the sensor for failure by checking continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should detect a resistance of approximately 1000 ohms in these areas. This is a typical 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. Good parts could be found in wrecking yards.