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 at the edge of transmission, above the flywheel gear. It sends a message to the ECU via a grey wire T55/49, then 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 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 signals to the G5 Tachometer located in 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 reached TDC and also the location of the camshaft to trigger the spark and injectors.
If this sensor fails, the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync and possibly indicating the chain stretching or a jump link on the upper timing chain. However, the code won't be displayed on its own without additional information from other sensors (G4 and G40).
It's a bit tricky to test because there are several pins on the connector, and they all have 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 operating at its maximum. Look for signs of coolant, or oil in the connector bay if there are issues with this part.
2. Injectors
Yesterday accelerating full speed from highway paytoll, I experienced massive power loss as if the engine was running out of gas or the injectors are not firing at all. In the morning, i removed the spark plugs, 3 were drenched with gazoline the fourth was dry. When I crank the engine with no sparks, i place a tissue on top of each injector hole, the 3 drenched with gazoline leap out, however the 4th stay closed. I tested the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. I think the issue is elsewhere.
I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it works fine when the G28 plugged in. However, the intermittent misfire problem persists at higher RPM. The coolant sensor (G62) even when unplugged, still shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is zero.
I'm not sure what to do. I think I've ruled everything else out. But i'm worried that I might have missed something. Please let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style transmitter is identical to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily find an extra in a wrecking shop or parts store. Test them out to do - just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black end of the connector). They should be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY) engines needs to know both the position and speed the crankshaft in order to make a decision about fuel injector timing, 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 the codes that could trigger the engine shutting down.
A damaged G28 sensor could result in an inaccurate speed counter for the gearbox and a gearbox which shifts faster than normal, and/or a misfire in the gear. If audi replacement key are experiencing any of these issues, it is most likely that your sensor is deteriorating and should be replaced. The good news is they are very cheap and readily available particularly in the case of an Bosch unit which is what ours are. Alternately, GM's version this part is an option.
5. Tachometer
A malfunctioning engine speed sensor could be the cause of many issues with your vehicle. It is an important part of the transmission of your Audi since it sends information to the ECU about how fast or slowly the engine is turning. This sensor can cause the transmission to fail and other components in the car to be affected.
The G5 engine speed sensor is situated on the outside of the transmission, above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 through an uncolored wire. The ECU uses this signal to control the amount of fuel and boost, as well as timig. It also relays it to the G5 Tachometer in instrument cluster. You can check 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 on pin T6a/1 (trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. It should show approximately 1000 ohms resistance between those points. This is a common feature across the Audi 80-100-200-RS2 model, ranging beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 Du So, you may find them in wrecking yards.