How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. This sensor is located near the transmission's edge just above the flywheel gear. It sends a message to the ECU through a grey wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission, above the flywheel ring gear G28 Engine Speed Sensor sends a signal to ECU pin T55/49 via the grey wire. The ECU uses this information to control boost and fuel. 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 must know when the crankshaft reached TDC and also the location of the camshaft to trigger the spark and injectors.
If this sensor fails, the ECU will throw a P00160 code which means the Crank Shaft and Intake Camshaft are out of sync and possibly indicating chain stretch or a jumped link on the upper timing chain. The code won't appear without the additional information supplied by other sensors (G4 or G40).
It can be a bit difficult to test since there are different pins on the connector, and they all have different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. It should read about 1000 ohms if the sensor is at full operation. If audi a3 replacement key are having problems with this part, check for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at a high speed I noticed a significant reduction in power. It was like the engine was running out of gas. Or my injectors were not firing. I pulled out the spark plugs this morning, three were soaked in gasoline, and the 4th was dry. When I crank the engine with no sparks, I put a piece of tissue on the top of each hole in the injector and the 3 that were drenched in gazoline jump out but the 4th stays shut. I checked the ground connection of ECU pins 14,30 and 48/55. I got zero ohm. I assume that the problem is elsewhere.
I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it works fine when the G28 plugged in. However, the intermittent misfire problem still occurs at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is 0.
I don't know what to do. I feel like i've pretty much all other possibilities out. However, i'm afraid that I might have missed something. If anyone has suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal sent 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 the spare in a salvage shop or a 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 end facing upwards). They should be infinite Ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that must know the speed and position of the crankshaft in order to make decisions about timing of the fuel injector, for example. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these sensors go badly, you will see codes on the diagnostic scanner that can cause the engine to shut down.
Some of the symptoms 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. If you experience any of these problems, it is likely that your sensor is deteriorating and requires replacement. The good thing is that they are very affordable and readily available particularly if you're looking at an Bosch model, like ours. Alternatively, GM's version of this part is a good option.
5. Tachometer
A malfunctioning engine speed sensor could be a cause for a slew of issues in your car. It is an important part of the transmission in your Audi, as it transmits information to the ECU regarding how fast or slowly the engine of the car is turning. This sensor could cause the transmission to malfunction and other components of the car to be affected.
The G5 engine speed sensor is located on the outside of the transmission, above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 via a grey wire. The ECU uses this signal to control the flow of fuel and boost and also timig. It also relays it to the G5 Tachometer in instrument cluster. You can test for sensor failure by examining the continuity of the sensor to the tachometer. Also, you can check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 as well as pin T26a/12. You should see a resistance of approximately 1000 ohms between these points. This is the same across the Audi 80-100-200-RS2 model, ranging from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 Du, so you might find them in wrecking yards.