4 Dirty Little Secrets About The Audi G28 Industry
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. The sensor is located near the transmission's edge, above the flywheel gear. It transmits a signal the ECU via a grey wire (T55/49), then to the tachometer within the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated at the edges of the transmission, directly above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU utilizes this information to regulate the amount of fuel and boost. It also sends an alert to the G5 Tachometer within 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 has reached TDC, and the location of the camshaft to trigger the spark and injectors.
If this sensor fails, the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync, possibly indicating chain stretch or a jumped link on 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).
Testing is a bit tricky as there are two different pins for the connector and they perform different functions however the best method of testing it is by measuring resistance between the sensor and the ECU. It should read approximately 1000 ohms when it is operating at its maximum. Check for signs of coolant or oil in the connector bay if you have problems with this part.
2. Injectors
Yesterday, while accelerating from the highway paytoll at a high speed I noticed a massive reduction in power. It was like the engine was running out of gas. Or, my injectors were not firing. This morning i pull out the spark plugs, three were soaked with gazoline and the 4th one was dry. I put a piece of tissue over each injector hole and when I start the engine with no sparks, the 3 that have gazoline pop 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'm assuming that the issue is elsewhere.
I also tried to reset PID without success. The car can start when the G28 is unplugged and it runs perfectly when it is plugged in but it still is experiencing intermittent misfires at higher RPM. The coolant sensor (G62) even when it is unplugged, shows temperatures of -49c. I also 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 believe that I've ruled everything else out. I'm afraid i may have missed something. If anyone has any ideas please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal from the RPM sensor. The GM-style transmitter is identical to the G4 and both are used in the 80 100, 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or in a local parts store. It is easy to test them - just put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). audi a3 key replacement must be infinite Ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that needs to know the speed and position of the crankshaft in order to make a decision about timing of the fuel injector, for example. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these goes badly, you will see codes on the diagnostic scanner that can lead to engine shutdown.
Some of the signs of a failing G28 sensor include an inaccurate rev counter in the gearbox, gears shifting quicker than normal and/or misfiring when you are in gear. It is probable that your sensor is failing and needs to be replaced if you encounter any of these signs. They are cheap and easy-to-find particularly if they're a Bosch model like ours. Alternately, GM's version this component is an option.
5. Tachometer
A malfunctioning engine sensor can cause a number of problems in your car. It's an essential component of the transmission in your Audi, as it transmits information to the ECU regarding how fast or slow the engine of the car is spinning. If this sensor fails, it can disrupt the performance of the transmission and the rest of the car's components.
The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It transmits a signal via a gray wire to the ECU pin T55/49. The ECU uses this signal to regulate the amount of fuel and boost, and also to timigrate. It also transmits it to the G5 Tachometer in instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. It should show approximately 1000 ohms of resistance between these two points. This is a typical part that is found across the Audi 80, 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU so good ones could be available in wrecking yards.