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 situated near the edges of the transmission just above the flywheel ring gear. It transmits a signal to the ECU via the grey wire T55/49 and then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated on the edge of transmission, directly above the flywheel ring. This sensor sends signals through the grey wire to pin T55/49. The ECU uses this information to control fuel and boost. visit the following website page sends a signal to the G5 Tachometer located in the instrument cluster.
The sensor is used to connect with 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 when it fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is not in sync with the Intake Camshaft. It could also indicate a chain stretch or a jumped chain link in the upper 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 because there are two connector pins and they serve different purposes but the best method of testing it is to measure resistance between the sensor and the ECU. If the sensor is operational, it should be reading around 1000 ohms. Examine for signs of coolant, or oil in the connector bay if there are problems with this part.
2. Injectors
Yesterday, while accelerating from the highway paytoll at a high speed I noticed a massive drop in power. It was like the engine had run out of gas. Or, my injectors weren't firing. Today, i pulled out the spark plugs, 3 were drenched in gazoline, the fourth was dry. I placed a tissue over each hole in the injector and when i turn the engine on without sparks, the ones that have gazoline pop right out. The fourth one remains shut. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I got 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 problem persists at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature of -49c, even if I unplug it. I also noticed that the oil pressure gauge in the cockpit is showing 2 bar while the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do, as i think i've pretty much completely ruled out all other possibilities. I'm afraid i may have missed something. Let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. It is easy to find the spare in a salvage shop or a parts store. It is easy to test them: simply put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines needs to know both the position and speed of the crankshaft in order to make a decision about timing of fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you have a problem with either of these sensors, the diagnostic scanner will show codes that could lead to the engine shutting down.
A damaged G28 sensor can cause an inaccurate gearbox speed counter and a gearbox which shifts faster than normal, and/or a misfire in gear. If you have any of these issues it is likely that your sensor is going bad and requires replacement. The good news is that they are very cheap and easy to find particularly in the case of a Bosch unit which is what ours are. Alternately, GM's version this part would be a good option.
5. Tachometer
A malfunctioning engine speed sensor could be the reason behind many issues in your car. It's an essential component of the transmission of your Audi since it sends information to the ECU about how fast or slowly the engine of the car is turning. When this sensor fails, it will disrupt the performance of the transmission and the other car's components.
The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It sends signals via a gray wire to the ECU pin T55/49. The ECU is then able to process this signal to control the flow of fuel, timig and boost as well as transmitting it to the G5 Tachometer located in the instrument cluster. You can determine if the sensor is in failure by examining the continuity from the sensor to the tachometer. Also, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [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 range, from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 DU, so you might find them in wrecking yards.