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. The sensor is located on the outside of the transmission, above the flywheel gear. It transmits a signal to the ECU via an uncolored wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
The sensor is located at the edge of the transmission, above the flywheel ring gear, the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through a grey wire. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends signals to the G5 tachometer inside 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 is TDC and where the camshaft is located so that it can activate spark and injectors accordingly.
If this sensor fails the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync and could indicate the chain stretching or a jump link on the upper timing chain. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).
Testing is a bit challenging as there are two different connector pins, and they have different functions however the best way to test it is to measure the resistance between the sensor and the ECU. When the sensor is operational, it should read about 1000 ohms. If you are having problems with this part, check for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at a high speed I noticed a significant reduction in power. It was as if the engine had run out of gas. Or my injectors were not firing. Today, i pulled out the spark plugs, three were soaked with gazoline and the fourth was dry. When I crank the engine, there are no sparks, i place a tissue on the top of each of the injector holes and the 3 drenched with gazoline jump out but the 4th stay closed. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found zero ohm. So i assume the problem is elsewhere.
I also tried to reset the PID but without success. The car website can start when the G28 is disconnected and is running fine when it is connected, but still has the intermittent misfire issue at higher RPM. The coolant sensor (G62), even when it is unplugged, shows a temperature of -49c. I also noticed that the oil pressure gauge in the cockpit is showing 2 bar when the actual pressure is 0.0 when i rev the engine.
I'm not sure what to do. I think I've ruled everything else out. But i'm worried that I may have missed something. If new audi car key anyone has 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 both are used in the 80, 100 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or in a local parts store. It is easy to test them: simply put your DMM into more info resistance mode and determine the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They should be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) more info engines must know both the position and speed of the crankshaft to make decisions regarding timing of the fuel injector, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these goes badly, you will see codes on the diagnostic scanner which can cause the engine to shut down.
Some of the symptoms of a failed G28 sensor include an inaccurate rev counter in the gearbox and gears that shift faster than normal and/or a misfire when you're in gear. It is probable that your sensor is failing and requires to be replaced if you experience any of these signs. They're cheap and easy to find especially when they're a Bosch website unit like ours. Alternatively, GM's version of this part would be an excellent choice.
5. Tachometer
A damaged engine sensor could cause a myriad of issues in your car. It's a crucial component of the transmission in your Audi since it sends information to the ECU about how fast or slowly the engine is spinning. This sensor could cause the transmission to malfunction and other car components to be affected.
The G5 engine sensor is located at the outskirts of the transmission, over the flywheel ring. It sends a signal via an uncolored wire to the ECU pin T55/49. The ECU utilizes this signal to control the flow of fuel and boost as well as timig. It also transmits it to the G5 Tachometer located in the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should detect the resistance to be around 1000 ohms between these points. This part is common across the Audi 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 Du So, you may find good ones in wrecking yards.