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, above the flywheel ring gear. It transmits a signal the ECU via the grey wire (T55/49) and then to the tachometer within the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission just above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through the grey 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 needs to know when the crankshaft reached TDC and also the position of the camshaft, so that it can activate the spark and injectors.
If this sensor fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jump in the chain link of the upper chain. The code won't show without the additional information supplied by other sensors (G4 or G40).
It's a bit tricky to test as there are various connector pins, and each has its own functions. audi q7 car key replacement to test it is to measure the resistance between the ECU and the sensor. It should read approximately 1000 ohms if the sensor is operating at its maximum. If you're having issues with this component, look for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, while accelerating from the highway paytoll at a high speed I noticed a significant 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, three were drenched in gasoline and the fourth was unclean. When I start the engine without sparks, I put a piece of tissue on the top of each hole in the injector, the 3 drenched with gazoline leap out, however the 4th one stays closed. I tried to test the ground connections of ECU pins 14,30 and 48/55. I got zero ohm. Therefore, i think the issue is somewhere else.
I also tried to reset the PID with no success. The car can start if the G28 is not plugged in and is running fine when it is connected however it 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 when the actual pressure is 0.0 when I crank up the engine.
I'm not sure what to do. I feel like i've pretty much eliminated everything else. However, i'm afraid that i might have missed something. Let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter is identical to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find an extra in a wrecking shop or parts store. It is simple to test them - just 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 of our 20vt turbo (3B AAN ABY ADU) engines needs to know the position and speed the crankshaft to make decisions regarding timing of the fuel injector, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these sensors go badly, you will see codes on the diagnostic scanner which can lead to engine shutdown.
Some of the symptoms of a malfunctioning G28 sensor are an inaccurate rev counter for the gearbox and gears that shift faster than normal and/or a misfire when you're in gear. It is likely that the sensor is failing and needs to be replaced if you encounter any of these symptoms. They are cheap and easy-to-find particularly in the case of a Bosch model like ours. Alternatively, GM's version of this part would be an option.
5. Tachometer
A faulty engine speed sensor could be a cause for numerous problems in your car. It's a vital component of your Audi's transmission, because it communicates to the ECU about how fast or slow the car's crankshaft is spinning. This sensor could cause the transmission to malfunction and other car components to be affected.
The G5 engine speed sensor is located on the edge of the transmission, above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 via a grey wire. The ECU is then able to process this signal to regulate fuel, timig, and boost, and also transmitting it to the G5 tachometer inside the 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. There should be a resistance of approximately 1000 ohms between these points. This is a standard component across the Audi 80 100 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.