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How to Replace an Audi G28 Engine Speed Sensor

Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. This sensor is located at the top of the transmission just above the flywheel ring gear. It transmits a signal to the ECU through a grey wire T55/49, then to the tachometer located on the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated on the edge of transmission, just above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU utilizes this information to control the amount of fuel and boost. It also sends a signal to the G5 Tachometer located in 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 reached TDC, and the position of the camshaft, in order to activate the spark and injectors.

If this sensor fails to function, the ECU will display an error code P00160. This indicates that the Crank Shaft is not in line with the Intake Camshaft. It could also be a sign of a chain stretch or a jumpy chain link in the upper chain. The code will not appear without the additional information supplied by other sensors (G4 or G40).

Testing is a bit tricky since there are two connector pins, and they have different functions but the most effective method of testing it is to measure resistance between the sensor and the ECU. It should read about 1000 ohms when the sensor is in full operation. Examine for signs of coolant or oil in the connector bay if you are experiencing issues with this component.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at full speed I noticed a massive decrease in power. It was like the engine was running out of gas. Or, my injectors were not firing. Today, i pulled out the spark plugs. Three were soaked with gazoline and the fourth one was dry. When I start the engine, there are no sparks i put tissue on top of each injector hole and the 3 drenched with gazoline leap out, however the 4th stays closed. I checked the ground connection of ECU pins 14,30 and 48/55. I found zero ohm. I'm assuming that the issue is in another location.

I also tried to reset the PID without success. The car can start when the G28 is disconnected and it runs perfectly when it is connected, but still is experiencing intermittent misfires at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is zero.

I'm not certain what to do, i feel i have pretty more info much completely ruled out all other possibilities. But i'm worried that i might have missed something. Please let me know should you have any suggestions! TIA!

3. Fuel Pump

The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style transmitter is identical to the G4 and both here function in the 80, 100 200, UrS and RS2 cars so you can easily find one at a wrecking yard or at a parts store. It is easy to test them - just switch your DMM into resistance mode and measure 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 check here an ECU that must know the position and speed of the crankshaft in order to make decisions regarding fuel injector timing etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either of these, the diagnostic scanner will display codes that could lead to the engine shutting down.

A damaged G28 sensor could result in an inaccurate speed counter for the gearbox or a gearbox that shifts faster than normal, or a misfire while in audi a4 spare key gear. It is possible that the sensor is failing and needs to be replaced if you experience any of these symptoms. They are cheap and easy-to-find, especially when they're a Bosch model like ours. Alternately, the GM version of this part is also a great option.

5. Tachometer

A faulty engine speed sensor could be the cause of many issues with your car. It is a crucial part of the Audi's transmission check here since it relays information to the ECU about how the car's crankshaft is spinning. If the sensor fails, it can disrupt the performance of the transmission as well as the rest of the car's components.

The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It transmits an electrical signal through gray wire to ECU pin T55/49. The ECU then uses and processes the signal to control fuel, timig and boost, and also transmitting it to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. Additionally, you can check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]), and between pin T6a/1 and pin T26a/12. There should be the resistance to be around 1000 ohms between these points. This is a typical component across the Audi 80, 100 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.