How to Replace an audi q7 replacement key A3 Spare Key (Canvas.Instructure.Com) G28 Engine Speed Sensor

In this video Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is located at the top of the transmission just above the flywheel ring gear. It sends a message 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 located on the outside of the transmission, directly above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU uses this information to control the amount of fuel and boost. It also sends signals to the G5 tachometer 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 located so that it can start spark and injectors accordingly.

If this sensor fails when it fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumped chain link in the upper chain of timing. However the code will not appear on its own, without additional information from other sensors (G4 and G40).

Testing is a bit challenging since there are two connector pins and they have different functions but the most effective way to test it is to measure the resistance between the sensor and the ECU. If the sensor is operational, it should read about 1000 ohms. If you're experiencing issues with this component, look for signs of oil or coolant in the connector bay.

2. Injectors

Yesterday, while accelerating from the highway paytoll at a high speed I noticed a significant decrease in power. It was like the engine had run out of gas. Or, my injectors weren't firing. This morning i pull out the spark plugs. Three were drenched in gazoline, the fourth one was dry. When I crank the engine, there are no sparks, I put a piece of tissue on top of each injector hole and the 3 drenched with gazoline leap out, however the 4th stays closed. I tested the ground connection of ECU pins 14,30 and 48/55. I got zero ohm. I assume that the problem is somewhere else.

I also tried to reset PID but without success. The car can start if the G28 is disconnected and runs fine when it is plugged in however it has the intermittent misfire issue at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature value of that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is zero.

I'm not sure what to do, as i feel i have pretty much ruled out everything else. But i'm worried that i might have missed something. If anyone has suggestions, please share them! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal sent by the RPM sensor. The GM-style sensor is identical to the G4 and they both work in the 80 100 200, UrS and RS2 cars which is why you can easily locate one at a junkyard or from a parts store. It is simple to test them - simply put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They should be infinite ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that needs to be aware of the speed and position of the crankshaft to make a decision about timing of the fuel injector, for example. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes badly, you will see codes on the diagnostic scanner which can lead to engine shutdown.

Some of the symptoms of a failing G28 sensor are an inaccurate gearbox rev counter, gears shifting quicker than normal, and/or a misfire when you're in gear. If you have any of these problems, it is likely that your sensor is deteriorating and should be replaced. They are cheap and easy-to-find particularly if they're a Bosch unit 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 many issues with your vehicle. It's a crucial component of the transmission of your audi q5 key because it relays information to the ECU regarding how fast or slow the engine is turning. This sensor could cause the transmission to malfunction and other components in the car to be affected.

The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It sends a signal via a gray wire to the ECU pin T55/49. The ECU utilizes this signal to control the flow of fuel and boost and also to timigrate. It also relays it to the G5 Tachometer inside the instrument cluster. You can test for sensor failure by checking continuity from the sensor to the tachometer. You can also 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. There should be a resistance of approximately 1000 ohms between these points. This is a standard component across the audi advance key 80 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.