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 situated near the edges of the transmission above the flywheel ring gear. It sends a message to the ECU through a grey wire T55/49, then to the tachometer on the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the edge of transmission, above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU uses this information to control boost and fuel. It also sends signals to the G5 Tachometer located in the instrument cluster.
The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu has to be aware of when the crankshaft has reached TDC, and the position of the camshaft, to trigger the spark and injectors.
If this sensor fails the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync and could indicate the chain stretching or a jump link on the upper chain of timing. The code won't appear without the additional information provided by other sensors (G4 or G40).
Testing is a bit challenging because there are two connector pins and they serve different purposes but the most effective method to test it is to measure the resistance between the sensor and the ECU. When the sensor is operational, it should read approximately 1000 ohms. If you are having problems with this sensor, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at full speed I noticed a massive drop 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 soaked in gasoline, and the 4th was dry. When I start the engine with no sparks, i place a tissue on top of each injector hole and the 3 that were drenched in gazoline leap out, however the 4th stays shut. I checked 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 not plugged in and is running fine when it is plugged in however it has the intermittent misfire issue 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 is showing 2 bar while the actual pressure is 0.0 when i rev the engine.
I'm not sure what to do, as i think i've pretty much eliminated everything else. I'm afraid i may have missed something. If anyone has any suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated more info by a signal from the RPM sensor. The GM-style transmitter is similar to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. It is easy to find the spare in a check here salvage shop or parts store. It is easy to test them - simply switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN check here ABY ADU) engines needs to know both the position and speed the crankshaft to make decisions regarding fuel injector timing, etc. In order to do this it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either one of these, the diagnostic scanner will display the codes that could trigger the engine shutting down.
Some of the symptoms of a malfunctioning G28 sensor are an inaccurate rev counter in the gearbox and gears that shift faster than normal and/or misfiring when you're in gear. If you experience any of these problems, it is likely your sensor is going bad and should be replaced. The good thing is that they are quite affordable and easily accessible, especially when you're looking at an Bosch model, which is what ours are. Alternately, the GM version of this component is also a good choice.
5. Tachometer
A failing engine sensor could cause a variety of issues within your vehicle. It's an essential component of the Audi's transmission as it sends information to the ECU about how fast or slow the vehicle's crankshaft is turning. This sensor could cause the transmission to malfunction and other components of the car to be affected.
The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It transmits signals via an uncolored wire to the ECU pin T55/49. The ECU uses this signal to control the amount of fuel and boost, and also timig. It also sends it to the G5 Tachometer inside the instrument cluster. You can test the click here sensor for failure by examining the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. There should be a resistance of approximately 1000 ohms between these two points. This is a common feature across the Audi 80-100-200-RS2 range, from the 1985 MC all the how to open audi car key way up to the 1997 UrS An and 1995 RS2 DU, so you might find good ones in wrecking yards.