How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. This sensor is situated near the transmission's edge, above the flywheel gear. It transmits a signal the ECU via the grey wire (T55/49) and then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The sensor is located at the edge of the transmission above the flywheel ring gear G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using an uncolored wire. The ECU utilizes this information to control fuel and boost. It also sends a signal to the G5 tachometer inside the instrument cluster.
The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft has reached TDC and also the position of the camshaft, in order to activate the spark and injectors.
If this sensor fails, the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync and possibly indicating the chain is stretched or a jump link on the upper timing chain. The code won't appear without the additional information supplied by other sensors (G4 or G40).
Testing can be a bit difficult because there are two pins for the connector and they perform different functions however the best way to test it is to measure resistance between the sensor and the ECU. It should read about 1000 ohms when it is at full operation. Look for evidence of coolant or oil in the connector bay if you are experiencing issues with this part.
2. Injectors
Yesterday, when accelerating from highway paytoll at maximum speed I noticed a massive drop 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, 3 were drenched with gazoline the fourth one was dry. I put tissue over each injector hole and when i start the engine without sparks, the 3 with gazoline jump out. The 4th one remains closed. I checked the ground connection of ECU pins 14,30 and 48/55. I got zero ohm. I'm assuming the issue is in another place.
I also tried to reset PID but without success. The car will start when the G28 is disconnected, but it works fine when the G28 plugged in. However, the intermittent misfire problem persists at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature value of -49c, even if I unplug it. Also i noticed that the gauge for oil pressure in the cockpit is showing 2 bar while the actual pressure is 0.0 when I crank up the engine.
I'm not sure what to do. I believe that I've ruled everything else out. But i'm worried that i might have missed something. If anyone has suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style transmitter is similar 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 easy to test them - simply put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing up). 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 decisions regarding timing of the fuel injector, for example. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either of these sensors, the diagnostic scanner will show codes that could cause the engine shutting down.
Some of the signs of a failed G28 sensor include an inaccurate rev counter for the gearbox, gears shifting quicker than normal and/or misfiring when you're in gear. It is probable that your sensor is failing and requires to be replaced if you encounter any of these signs. They are cheap and easy-to-find particularly when they're an Bosch model like ours. If audi a3 key fob replacement prefer, GM's version of this part is an option.
5. Tachometer
A failing engine speed sensor could be the cause of many problems in your vehicle. It's an essential component of the transmission in your Audi because it relays information to the ECU on how fast or slow the car's engine is spinning. When this sensor fails, it can disrupt the performance of the transmission, as well as the other car's components.
The G5 engine speed sensor is located on the outside of the transmission just above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 via a grey wire. The ECU is then able to process this signal to control the flow of fuel, timig and boost as well as sends it on to the G5 tachometer inside the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see around 1000 ohms of resistance between these two points. This is a common feature across the Audi 80-100-200-RS2 model, ranging beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 DU So, you may find good ones in wrecking yards.