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 near the edges of the transmission just above the flywheel ring gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 via a grey wire. The ECU utilizes this information to control boost and fuel. It also sends signals 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 be aware when the crankshaft is TDC and the location of the camshaft so it can trigger spark and injectors according to the situation.
If this sensor fails when it fails, the ECU will display an error code P00160. This means that the Crank Shaft is out of line with the Intake Camshaft. It could also be a sign of an issue with the chain or a jumpy chain link in the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40).
Testing is a bit tricky because there are two connector pins, and they serve different purposes but the best method of testing it is to measure the resistance between the sensor and the ECU. When the sensor is fully operational, it should be reading around 1000 ohms. If you're having issues with this component, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, while accelerating from the highway paytoll at maximum speed, i noticed a huge drop in power. It was like the engine was running out of gas. Or, my injectors weren't firing. In the morning, i removed the spark plugs, three were drenched with gazoline the fourth was dry. I placed a tissue over each hole in the injector and when I start the engine with no sparks, the ones that have gazoline pop right out. The fourth one remains closed. I checked the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. I assume that the problem is elsewhere.
I also tried to reset the PID but without success. The car will start when the G28 is disconnected and is running fine when it is connected but it still has the intermittent misfire issue at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature of -49c, even if I unplug it. I also more info noticed that the gauge for oil pressure in the cockpit shows 2 bar when the actual pressure is 0.0 if i crank up the engine.
I'm not certain what to do, as i feel i have pretty much ruled out everything else. I'm afraid i may have missed something. Let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter is identical to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find a spare in a wrecking shop or here 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 about timing of the fuel injector, for example. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve get more info this. If either of these goes bad you will get codes on the diagnostic scanner that can cause the engine to shut down.
A malfunctioning G28 sensor could result in an inaccurate gearbox speed counter or a gearbox that shifts more quickly than normal, and/or a misfire in the gear. If you experience any of these issues it is likely your sensor is deteriorating and needs replacing. They're cheap and easy get more info to find, especially when they're a Bosch unit like ours. Alternatively, GM's version of this part would be an option.
5. Tachometer
A malfunctioning engine sensor can cause a number of problems in your vehicle. It's an essential component of your Audi's transmission, because it communicates to the ECU about how fast or slow the car's crankshaft is spinning. This sensor could cause the transmission to fail and other components in read more the car to be affected.
The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It transmits an electrical signal through an uncolored wire to the ECU pin T55/49. The ECU then uses and processes the signal to control fuel, timig and boost, and also transmitting it to the G5 tachometer in the instrument cluster. You can test for sensor failure by checking continuity from the sensor to the tachometer. Additionally, you can check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]) and between pin T6a/1 as well as pin T26a/12. You should detect the resistance to be around 1000 ohms between these two points. This is a common feature across the Audi 80-100-200-RS2 range, beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 DU, so you might find some good ones in wrecking yards.