How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. The sensor is located on the outside of the transmission over the flywheel gear. It transmits a signal to the ECU through an uncolored wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using a grey wire. The ECU utilizes this information to regulate fuel and boost. It also sends signals to the G5 tachometer inside the instrument cluster.
audi advanced key is used to connect 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 trigger spark and injectors accordingly.
If this sensor fails, the ECU will throw the P00160 error, which means the Crank Shaft and Intake Camshaft are out of sync, possibly indicating the chain is stretched or a jump link on the upper timing chain. However the code will not appear on its own, without additional information from other sensors (G4 and G40).
Testing can be a bit difficult since there are two pins for the connector and they have different functions however the best method to test it is by measuring resistance between the sensor and the ECU. It should read around 1000 ohms if the sensor is at full operation. Look for evidence of coolant or oil in the connector bay if you are experiencing issues with this part.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at maximum speed, i noticed a huge drop in power. It was like the engine had run out of gas. Or, my injectors were not firing. I pulled out the spark plugs this morning and found that 3 were drenched in gasoline and the 4th was dry. When I crank the engine with no sparks i put tissue on the top of each hole in the injector and the 3 drenched with gazoline leap out, however the 4th stay shut. I inspected the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ i get zero ohm. I assume that the problem is elsewhere.
I also tried to reset the PID but with no luck. The car will start when the G28 is disconnected, but it is running fine with the G28 plugged in. However the intermittent misfire issue persists at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature of that is -49c even after unplugging it. audi advanced key noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is zero.
I don't know what to do. I believe that I've eliminated everything else. However, i'm afraid that I may have missed something. If anyone has any suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal from 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 locate a spare in a wrecking shop or a parts store. It is simple to test them - just switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines have an ECU that has to know the position and speed of the crankshaft in order to make a decision about timing of the fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either of these sensors, the diagnostic scanner will display codes that could cause the engine shutting down.
The signs of a malfunctioning G28 sensor are an inaccurate gearbox rev counter the gears are shifting faster than normal, and/or a misfire when you're in gear. If you are experiencing any of these issues, it is most likely that your sensor is going bad and needs replacing. The good thing is that they are very affordable and easy to find particularly when you're looking at an Bosch unit which is what ours are. You can also choose the GM version of this unit is also a good choice.
5. Tachometer
A faulty engine speed sensor could be the reason behind a slew of problems in your car. It's a vital component of the Audi's transmission since it relays information to the ECU about how fast or slow the car's crankshaft is turning. This sensor could cause the transmission to malfunction and other car components to be affected.
The G5 engine speed sensor is located on the edge of the transmission, above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49, via a grey wire. The ECU then uses and processes this signal to regulate the flow of fuel, timig and boost, and also transmitting it to the G5 tachometer inside the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. It should show approximately 1000 ohms resistance between those 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 1995 RS2 Du, so you might find some good ones in wrecking yards.