How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. The sensor is situated at the top of the transmission above the flywheel ring gear. It transmits a signal the ECU via the grey wire (T55/49) which is then sent to the tachometer within 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 uses this information to regulate boost and fuel. It also sends an indication to the G5 tachometer in the instrument cluster.
The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must be aware of when the crankshaft has reached TDC and also the location of the camshaft to trigger the spark and injectors.
If this sensor fails the ECU will throw the P00160 error, which means 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 error code won't appear on its own without additional information from other sensors (G4 and G40).
Testing is a bit challenging because there are two pins for the connector and they serve different purposes but the best way to test it is to measure resistance between the sensor and the ECU. If the sensor is operational, it should read approximately 1000 ohms. If you're experiencing issues with this part, check for signs of coolant or oil in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at a high speed I noticed a massive reduction in power. It was as if the engine was running out of gas. Or my injectors weren't firing. I took out the spark plugs this morning, 3 were drenched in gasoline and the fourth was dry. I placed a tissue over each hole in the injector and when I start the engine without sparks, the ones with gazoline jump right out. The fourth one remains shut. I checked the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. I assume that the problem is somewhere else.
I also tried to reset the PID but without success. The car is able to start if the G28 is disconnected and it runs perfectly when it is plugged in however it is experiencing intermittent misfires at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0.
I don't know what to do. I think I've eliminated everything else. I'm afraid i may have missed something. Please let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. It is easy to find a spare in a wrecking shop or a parts store. It is simple to test them - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's side). They should be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines must know the position and speed of the crankshaft to determine timing of fuel injectors, etc. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either one of these, the diagnostic scanner will display the codes that could trigger an engine shutdown.
Some of the signs of a failed G28 sensor include an inaccurate rev counter in the gearbox the gears are shifting faster than normal and/or a misfire when you're in gear. If more.. experience any of these issues, it is likely that your sensor is going bad and requires replacement. The good thing is that they are quite affordable and easily accessible, especially if you're looking at the Bosch unit which is what we have. If you prefer, GM's version of this component is an excellent choice.
5. Tachometer
A malfunctioning engine sensor can cause a variety of issues in your vehicle. It's a crucial component of the transmission in your Audi since it sends information to the ECU on how fast or slow the engine is turning. If the sensor fails, it could affect the performance of the transmission, as well as the rest of the car's components.
The G5 engine speed sensor is located at the edge of the transmission just above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU utilizes this signal to regulate the amount of fuel and boost, and also timig. It also transmits it to the G5 Tachometer located in the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should observe around 1000 ohms of resistance between those two pins. This is a standard part that is found 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 parts could be found in wrecking yards.