How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. This sensor is situated at the edge of transmission over the flywheel gear. It sends a signal to the ECU via an uncolored wire (T55/49) which is then sent to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission above the flywheel ring gear, the G28 Engine Speed Sensor sends signals to ECU pin T55/49 via an uncolored wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends a signal to the G5 tachometer in the instrument cluster.
The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is so it can start spark and injectors according to the situation.
If this sensor fails the ECU will throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync and could indicate the chain stretching or a jump link on the upper chain of timing. The code will not appear without the additional information supplied by other sensors (G4 or G40).
Testing is a bit tricky as there are two different pins for the connector and they serve different purposes but the most effective method of testing it is by measuring resistance between the sensor and the ECU. If the sensor is operational, it should be reading around 1000 ohms. Check for signs of coolant or oil in the connector bay if you have issues with this component.
2. Injectors
Yesterday, when i was accelerating to the fullest speed from highway paytoll, I experienced a big cut in power as if the engine was running out of gas or injectors aren't firing any more. This morning i pull out the spark plugs, 3 were drenched in gazoline, the fourth one was dry. I put tissue over each injector hole and when I start the engine with no sparks, the three with gazoline jump out. The fourth one remains shut. I tested the ground connection of ECU pins 14,30 and 48/55. audi key programming near me got zero ohm. Therefore, i think the issue is elsewhere.
I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it works fine when the G28 connected. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62), even when it is unplugged, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is zero.
I'm not certain what to do, as i believe that i've eliminated everything else. I'm afraid i may have missed something. Please let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style sender is identical to the G4 and they both work in the 80 100 200, UrS and RS2 cars which is why you can easily locate one at a junkyard or in a local parts store. Test them out - put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black end of the connector). They should be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that must be aware of the speed and position of the crankshaft in order to make decisions about timing of the fuel injector, for example. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go badly, you will see codes on the diagnostic scanner which can lead to engine shutdown.
Some of the signs of a malfunctioning G28 sensor include an inaccurate rev counter for the gearbox, gears shifting quicker than normal and/or misfiring when in gear. If you are experiencing any of these issues it is most likely that your sensor is deteriorating and should be replaced. They are cheap and easy-to-find especially if they're a Bosch unit like ours. Alternatively, the GM version of this component is also a great option.
5. Tachometer
A failing engine sensor could cause a myriad of issues within your vehicle. It's a crucial component of the transmission in your Audi, as it transmits information to the ECU regarding how fast or slowly the engine is turning. This sensor could cause the transmission to fail and other components in the car to be affected.
The G5 engine sensor is located at the outskirts of the transmission, just above the flywheel ring. It transmits a signal via an uncolored wire to the ECU pin T55/49. The ECU uses this signal to regulate the flow of fuel and boost and also timig. It also relays it to the G5 Tachometer inside the instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should observe approximately 1000 ohms resistance between those points. This part is common across the Audi 80-100-200-RS2 model, ranging beginning with the 1985 MC and up to the 1997 UrS AN and the 1995 RS2 Du You may also find them in wrecking yards.