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 situated on the edge of the transmission above the flywheel ring gear. It transmits a signal the ECU via an uncolored wire (T55/49) which is then sent to the tachometer in 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 an electrical signal to ECU pin T55/49 via 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 serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can start spark and injectors in the right way.
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 chain stretch or a jumped 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 is a bit tricky because there are two pins for the connector and they perform different functions but the most effective method to test it is to measure resistance between the sensor and the ECU. It should read around 1000 ohms when the sensor is at full operation. If you are having problems with this component, look for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at a high speed I noticed a massive decrease in power. It was like the engine was running out of gas. Or my injectors were not firing. This morning i pull out the spark plugs, three were drenched with gazoline the fourth one was dry. When i crank the engine, there are no sparks, i place a tissue on top of each injector hole, the 3 drenched with gazoline jump out but the 4th one stays shut. I checked the ground connection of ECU pins 14,30 and 48/55. I got zero ohm. So i assume the problem is elsewhere.
I also tried to reset PID without success. The car will start when the G28 is disconnected and it runs perfectly when it is connected but it still has the intermittent misfire issue at more info higher RPM. The coolant sensor (G62) even if it is not plugged in, shows a temperature of -49c. Also i noticed that the gauge for oil pressure in the cockpit shows 2 bar when the actual pressure is 0.0 when I crank up the engine.
I'm not certain what to do, as i feel i have pretty much eliminated everything else. I'm concerned that i may have missed something. If anyone has any check here ideas please chime in! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal by 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 salvage yard or at a parts store. It is simple to test them - simply 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 should be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines have an ECU that click here has to be aware of the speed and position of the crankshaft in order to make decisions regarding timing of the fuel injectors, etc. In order to do this it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these, the diagnostic scanner will show codes that could lead to an engine shut down.
A malfunctioning G28 sensor could cause an inaccurate speed counter for the gearbox or a gearbox that shifts faster than normal, or an unfire when in the gear. If you are experiencing any of these problems, it is most likely that your sensor is going bad and needs replacing. The good news is they are quite affordable and readily available particularly if you're looking at a Bosch sensor, like ours. You can also choose the GM version of this unit is also a good option.
5. Tachometer
A faulty engine speed sensor could be a cause for many issues with your car. It's an essential component of your Audi's transmission, as it sends get more info information to the ECU about how the car's crankshaft is spinning. If this sensor fails, it can cause problems for the transmission as well as the other car's components.
The G5 engine speed sensor is situated on the edge of here the transmission, above the flywheel ring gear and sends a signal to the ECU at pin T55/49, via a grey wire. The ECU is then able to process this signal to regulate the flow of fuel, timig and boost, and also sends it on to the G5 tachometer in the instrument cluster. You can test for sensor failure by checking continuity from the sensor to the tachometer. You can also examine the continuity between pins 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 part is common across the Audi 80-100-200-RS2 model, ranging 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.