How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. The sensor is located at the edge of transmission, above the flywheel gear. It sends a signal to the ECU via a grey wire (T55/49), then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The sensor is located at the edge of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via the grey wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends an indicator to the G5 Tachometer in instrument cluster.
The sensor is used to connect with the G40 Camshaft position Sensor. The ecu must know when the crankshaft reached TDC and also the location of the camshaft so that it can activate the spark and injectors.
If this sensor fails, the ECU will display a P00160 error code. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also indicate a chain stretch or a jumped chain link in the upper chain. The code won't appear without the additional information provided by other sensors (G4 or G40).
Testing is a bit challenging since there are two connector pins, and they perform different functions but the most effective method of testing it is by measuring resistance between the sensor and the ECU. When the sensor is functional, it should read around 1000 ohms. If you are having problems with this component, look for evidence of oil or coolant in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at maximum speed I noticed a significant decrease in power. It was as if the engine was running out of gas. Or my injectors were not firing. Today, i pulled out the spark plugs, 3 were soaked with gazoline and the fourth was dry. I placed a tissue over each injector hole, and when i start the engine with no sparks, the 3 with gazoline jump right out. The fourth one remains shut. I tested the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. Therefore, i think the issue is somewhere else.
I also tried to reset the PID but with no luck. The car can start when the G28 is disconnected and runs fine when it is connected however it has intermittent misfire issues at higher RPM. The coolant sensor (G62), even when it is unplugged, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0.
I'm not certain what to do, i feel i have pretty much eliminated everything else. However, i'm afraid that i might have missed something. If anyone has any suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal by the RPM sensor. The GM-style transmitter is identical to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. It is easy to find the spare in a salvage shop or a parts store. Testing them is easy by putting your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black end of the connector). They must be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines needs to know the position and speed the crankshaft in order to make a decision about timing of the fuel injector, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these go bad you will get codes on the diagnostic scanner which can lead to engine shutdown.
Some of the signs of a failing G28 sensor include an inaccurate rev counter for the gearbox the gears are shifting faster than normal and/or misfiring when you're in gear. If you are experiencing any of these issues it is most likely that your sensor is deteriorating and needs replacing. The good thing is that they are quite affordable and easy to find, especially in the case of the Bosch model, like ours. Alternately, the GM version of this part is also a good choice.
5. Tachometer
A malfunctioning engine speed sensor could be the reason behind a slew of issues in your car. It is an important part of the transmission of your Audi because it relays information to the ECU regarding how fast or slowly the car's engine is spinning. If this sensor fails, it could cause problems for the transmission, as well as the other car's components.
The G5 engine speed sensor is situated on the outside of the transmission just above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 through an uncolored wire. The ECU uses this signal to regulate fuel and boost, as well as timig. It also relays it to the G5 Tachometer located in the instrument cluster. You can determine if the sensor is in failure by examining the continuity of 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 [79trace [79]) and between pin T6a/1 and pin T26a/12. G28CarKeys should detect the resistance to be around 1000 ohms in these areas. This is a standard part across the Audi 80, 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best ones could be available in wrecking yards.