How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is situated on the edge of the transmission above the flywheel ring gear. It transmits a signal to the ECU via an uncolored wire (T55/49), then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located at the edges of the transmission, directly above the flywheel ring. This sensor sends a signal via the grey wire to pin T55/49. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends an indicator to the G5 Tachometer within the instrument cluster.
The sensor is used to connect with the G40 Camshaft position Sensor. The ecu must be aware 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, the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync and possibly indicating the chain stretching or a jump link on the upper timing chain. However, the code won't appear on its own, without additional information from other sensors (G4 and G40).
It is a little tricky to test since there are different pins on the connector, and each has its own functions. The best way to do it is by measuring the resistance between the ECU and the sensor. It should read about 1000 ohms when the sensor is at full operation. If you're experiencing issues 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 full speed I noticed a significant reduction in power. It was like the engine was running out of gas. Or, my injectors weren't firing. I took out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was unclean. I put a piece of tissue over each injector hole, and when i turn the engine on without sparks, the three that have gazoline pop right out. The 4th one stays closed. I tested the ground connection of ECU pins 14,30, and 48/55. advanced key audi found 0ohm. So i assume the problem is elsewhere.
I also tried to reset the PID with no success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However, the intermittent misfire problem still occurs at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature of that is -49c even after unplugging it. Also, i noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.
I'm not sure what to do, as i feel i have pretty much ruled out everything else. I'm worried that i might have missed something. Please let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style transmitter is the same as the G4 and they both work in the 80 100 200, UrS and RS2 cars so you can easily find one at a salvage yard or from a parts store. It is simple to test them - just put 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 have an ECU that has to be aware of the speed and position of the crankshaft in order to make a decision about timing of the fuel injectors, etc. It makes use of 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.
The signs of a failed G28 sensor include an inaccurate rev counter in the gearbox the gears are shifting faster than normal, and/or a misfire when in gear. If you are experiencing any of these issues it is likely that your sensor is deteriorating and should be replaced. The good thing is that they are very affordable and readily available particularly when you're looking at the Bosch sensor, which is what we have. Alternatively, GM's version of this component is an excellent choice.
5. Tachometer
A failing engine sensor could cause a variety of issues in your vehicle. It's a crucial component of the transmission of your Audi, as it transmits information to the ECU on how fast or slow the engine of the car is turning. This sensor can cause the transmission to malfunction and other car components to be affected.
The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It sends a signal via an uncolored wire to the ECU pin T55/49. The ECU is then able to process this signal to control fuel, timig and boost and then transmitting it to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by examining the continuity of the sensor to the tachometer. Additionally, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 and pin T26a/12. There should be the resistance to be around 1000 ohms between these points. This part is common across the Audi 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS AN and the 1995 RS2 Du You may also find some good ones in wrecking yards.