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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 near the transmission's edge just above the flywheel gear. It sends a message to the ECU via a grey wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated at the edges of the transmission, above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU utilizes this information to regulate boost and fuel. It also sends an indication to the G5 Tachometer in instrument cluster.
The sensor is used to link with the G40 Camshaft position Sensor. The ecu needs to know 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 a P00160 error message. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also be a sign of an issue with the chain or a jump in the chain link of the upper chain of timing. However, the error code won't be displayed 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 they all have different functions. The best way to do it is to measure the resistance between the ECU and the sensor. It should read about 1000 ohms if the sensor is operating at its maximum. Check for signs of coolant, or oil in the connector bay if there are issues with this part.
2. Injectors
Yesterday, while accelerating from the highway paytoll at full speed I noticed a significant decrease in power. It was like the engine had run out of gas. Or my injectors were not firing. I took out the spark plugs this morning and found that 3 were drenched in gasoline and the 4th was dry. When i crank the engine, there are no sparks i put tissue on top of each injector hole and the 3 drenched with gazoline leap out, however the 4th one stays closed. I tested the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. Therefore, i think the issue is elsewhere.
I also tried to reset the PID but without success. The car can start when the G28 is unplugged and is running fine when it is connected, but still has intermittent misfire issues at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is 0.
I'm not sure what to do. I think I've eliminated everything else. But i am afraid i might have missed something. If anyone has any suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal sent by the RPM sensor. replacement audi key -style sensor is identical to the G4 and they both work in the 80 100, 200, UrS and RS2 cars so you can easily find one at a junkyard or in a local parts store. It is simple to test them - just put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that has to know the speed and position of the crankshaft to make a decision about fuel injector timing etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go badly, you will see codes on the diagnostic scanner which could cause engine shut down.
A malfunctioning G28 sensor could cause an inaccurate gearbox speed counter, a gearbox that shifts more quickly than normal, or an unfire when in the gear. If you are experiencing any of these issues it is likely your sensor is going bad and needs replacing. They're inexpensive and easy to locate especially when they're a Bosch model like ours. Alternatively, the GM version of this component is also a good option.
5. Tachometer
A damaged engine sensor could cause a number of problems in your vehicle. It's an essential component of the transmission in your Audi since it sends information to the ECU regarding how fast or slowly the car's engine is spinning. This sensor could cause the transmission to malfunction and other car components to be affected.
The G5 engine speed sensor is situated on the edge of the transmission just above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 via an uncolored wire. The ECU utilizes this signal to control the flow of fuel and boost as well as timig. It also relays it to the G5 Tachometer in instrument cluster. You can check the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. It should show approximately 1000 ohms of resistance between those points. This is a typical part across the Audi 80 100 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.