How to Replace an Audi G28 Engine Speed Sensor
In this video, Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is located at the top of the transmission just above the flywheel ring gear. It transmits a signal the ECU via a grey wire (T55/49) which is then sent to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated on the edge of transmission, above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an indication to the G5 Tachometer in instrument cluster.
The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can trigger spark and injectors in the right way.
If this sensor fails to function, the ECU will display a P00160 error message. This indicates that the Crank Shaft is not in sync with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumped chain link in the upper chain of timing. The code won't appear without the additional information supplied by other sensors (G4 or G40).
It is a little tricky to test because there are various pins on the connector, and each one has different functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. If the sensor is operational, it should be reading around 1000 ohms. If replacement car key audi are having problems with this component, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, while accelerating at full speed from the highway paytoll, I experienced massive power loss like the engine is running out of gas or the injectors are not firing anymore. I took out the spark plugs this morning and found that 3 were soaked in gasoline, and the fourth was dry. When i crank the engine, there are no sparks, i place a tissue on the top of each of the injector holes, the 3 drenched with gazoline pop out, but the 4th one stays closed. I tried to test the ground connections of ECU pins 14,30, and 48/55. I found zero ohm. I think the issue is elsewhere.
I also tried to reset the PID but with no luck. The car will start when the G28 is unplugged, and it is running fine with the G28 connected. However, the intermittent misfire problem still occurs at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0.
I'm not certain what to do, i think i've pretty much eliminated everything else. But i'm worried that I might have missed something. If anyone has any ideas please chime in! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal from the RPM sensor. The GM-style transmitter is similar to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or a parts store. Testing them is easy - put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black end of the connector). They must be infinite ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines must be aware of the position and speed of the crankshaft to determine timing of the fuel injector, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you encounter a problem with either of these, the diagnostic scanner will display codes that could lead to an engine shut down.
Some of the symptoms of a failing G28 sensor are an inaccurate rev counter in the gearbox and gears that shift faster than normal and/or a misfire when you are in gear. If you experience any of these issues it is likely your sensor is going bad and requires replacement. They are cheap and easy-to-find particularly when they're an Bosch sensor like ours. Alternately, GM's version this part would be a good option.
5. Tachometer
A failing engine sensor could cause a variety of issues in your vehicle. It is a crucial part of your Audi's transmission, because it communicates to the ECU about how fast or slow the vehicle's crankshaft is spinning. This sensor could cause the transmission to fail and other components of the car to be affected.
The G5 engine speed sensor is situated on the edge of the transmission, above the flywheel ring gear. It sends a signal to the ECU at pin T55/49 via a grey wire. The ECU then processes this signal to control the flow of fuel, timig and boost as well as transmitting it to the G5 tachometer inside the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between the 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. You should detect a resistance of approximately 1000 ohms between these two points. This is a common feature across the Audi 80-100-200-RS2 series, starting from the 1985 MC up to the 1997 UrS AN and 1995 RS2 Du, so you might find some good ones in wrecking yards.