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. This sensor is situated near the transmission's edge over the flywheel gear. It transmits a signal to the ECU via an uncolored wire (T55/49) and then to the tachometer within the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission, above the flywheel ring gear G28 Engine Speed Sensor sends a signal to ECU pin T55/49 through the grey wire. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends a signal to the G5 Tachometer located in the instrument cluster.

The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can trigger spark and injectors according to the situation.

If this sensor fails the ECU will display the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync and could indicate the chain is stretched or a jump link on the upper chain of timing. However, the code won't appear on its own, without additional information from other sensors (G4 and G40).

Testing can be a bit difficult because there are two connector pins and they perform different functions but the best way to test it is by measuring resistance between the sensor and the ECU. If the sensor is functional, it should read around 1000 ohms. If you are having problems with this sensor, look for signs of oil or coolant in the connector bay.

2. Injectors

Yesterday, while accelerating from the highway paytoll at full speed I noticed a significant decrease in power. It was as if the engine was running out of gas. Or my injectors weren't firing. This morning i pull out the spark plugs. Three were drenched in gazoline, the 4th one was dry. I placed a tissue over each injector hole, and when i start the engine with no sparks, the 3 with gazoline jump out. The 4th one stays closed. I checked the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. I think the issue is in another location.

I also tried to reset the PID with no success. The car is able to start if the G28 is not plugged in and is running fine when it is plugged in, but still is experiencing intermittent misfires at higher RPM. The coolant sensor (G62) even when it is unplugged, shows a temperature of -49c. Also i noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when i rev the engine.

I'm not certain what to do, as i feel i have pretty much ruled out everything else. I'm worried that i might have missed something. If anyone has suggestions, please let me know! 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 the same as the G4 and both are used in the 80, 100, 200, UrS and RS2 cars so you can easily find one at a wrecking yard or in a local parts store. It is simple to test them - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black connector's side). They should be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with here an ECU that must know the position and speed of the crankshaft to make a decision about timing of the fuel injectors, etc. 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 sensors, the diagnostic scanner will display codes that could cause the engine shutting down.

A failing G28 sensor could cause an inaccurate speed counter for the gearbox, a gearbox that shifts faster than normal, or a misfire in the gear. If you experience any of these problems, it is most likely that your sensor is failing and needs replacing. The good news is that they are quite affordable and easily accessible particularly when you're looking at an Bosch model, like ours. Alternately, the GM version of this component is also a great option.

5. Tachometer

A faulty engine speed sensor could be a cause for numerous issues with your vehicle. It's an essential component of the Audi's transmission because it communicates to the ECU about how fast or slow the car's crankshaft click here is rotating. If this sensor fails, it could affect the performance of the transmission as well as the rest of the car's components.

The G5 engine speed sensor is located at the edge of the transmission, above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 through an audi advanced key uncolored wire. The ECU uses this signal to regulate the flow of fuel and boost and also timig. It also transmits it to the G5 Tachometer inside the instrument cluster. You can check for sensor failure read more by checking continuity from the sensor to the tachometer. Additionally, 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 check here pin T26a/12. You should see the resistance to be around 1000 ohms between these two points. This is a common feature across the Audi 80-100-200-RS2 range, beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 DU, so you might find some good ones in wrecking yards.