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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. This sensor is located near the edges of the transmission, above the flywheel ring gear. It transmits a signal the ECU via an uncolored 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 the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 via the grey wire. The ECU utilizes this information to regulate boost and fuel. It also sends an indicator to the G5 Tachometer in instrument cluster.
The sensor is used to link the G40 Camshaft position Sensor. The ecu must know when the crankshaft reached TDC, and the position of the camshaft, so that it can activate the spark and injectors.
If this sensor fails the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft are out of sync and could indicate the chain is stretched or a jump link on the upper timing chain. The code won't appear without the additional information provided by other sensors (G4 or G40).
It's a bit tricky to test since there are several pins on the connector and each one has different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. It should read around 1000 ohms when it is at full operation. If you're having issues with this component, look for signs of coolant or oil in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at maximum speed I noticed a massive drop in power. It was as if the engine was running out of gas. Or, my injectors were not firing. In the morning, i removed the spark plugs, three were drenched with gazoline the fourth one was dry. I put tissue over each hole in the injector and when i turn the engine on without sparks, the ones with gazoline jump right out. The fourth one remains shut. I tested the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ i get zero Ohm. So i assume the problem is in another place.
I also tried to reset the PID but with no luck. The car will start when the G28 is disconnected, but it runs fine with the G28 plugged in. However, the intermittent misfire problem still occurs at higher RPM. audi a1 car key G28CarKeys (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 but the actual pressure is zero.
I'm not sure what to do. I believe that I've eliminated everything else. However, i'm afraid that I might have missed something. If anyone has any suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals from the RPM sensor. The GM-style transmitter 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 from a parts store. Testing them is easy - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black connector's end). They should be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines are equipped with an ECU that needs to know the speed and position of the crankshaft to make decisions about timing of the fuel injector, for example. To accomplish this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes wrong, you will receive codes on the diagnostic scanner that can lead to engine shutdown.
Some of the signs of a malfunctioning G28 sensor include an inaccurate gearbox rev counter, gears shifting quicker than normal and/or a misfire when you are in gear. It is likely that your sensor is failing and needs to be replaced if you notice any of these symptoms. The good news is they are very affordable and readily available, especially if you're looking at the Bosch model, which is what ours are. Alternately, GM's version this component is a good option.
5. Tachometer
A malfunctioning engine speed sensor could be the reason behind many issues in your car. It is a crucial part of your Audi's transmission, as it sends information to the ECU about how the car's crankshaft 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 near the edge of the transmission, just above the flywheel ring. It sends a signal via a gray wire to the ECU pin T55/49. The ECU uses this signal to regulate the flow of fuel and boost and also to timigrate. It also relays it to the G5 Tachometer in instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see around 1000 ohms of resistance between those two pins. This is a standard component across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU, so the best ones might be availble in wrecking yards.