How to Replace an audi q7 key G28 Engine Speed Sensor

Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is situated at the top of the transmission just above the flywheel ring gear. It transmits a signal to the ECU via a grey wire (T55/49) and then to the tachometer within the instrument cluster.

1. Engine Speed Sensor

The sensor is located at the edge of the transmission, above the flywheel ring gear, the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via a grey wire. The ECU uses this information to control fuel and boost. It also sends signals to the G5 tachometer inside the instrument cluster.

The sensor is used to link the G40 Camshaft position Sensor. The ecu must know when the crankshaft has reached TDC and also the position of the camshaft, so that it can activate the spark and injectors.

If this sensor fails, the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft are not in sync and could indicate chain stretch or a jumped link on the upper timing chain. The code won't show without the additional information provided by other sensors (G4 or G40).

It can be a bit difficult to test as there are different pins on the connector and each one has different functions. The best method for doing this is to measure the resistance between the ECU and the sensor. It should read around 1000 ohms if the sensor is in full operation. Look for evidence of coolant or oil in the connector bay if there are issues with this component.

2. Injectors

Yesterday, while accelerating from the highway paytoll at maximum speed I noticed a significant drop in power. It was like the engine had run out of gas. Or my injectors weren't firing. Today, i pulled out the spark plugs, 3 were soaked with gazoline and the fourth was dry. I put tissue over each injector hole, and when I start the engine without sparks, the three with gazoline jump out. The fourth one remains closed. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. i get zero Ohm. I think the issue is in another location.

I also tried to reset the PID without success. The car will start when the G28 is disconnected, but it runs fine with the G28 plugged in. However, the intermittent misfire problem persists at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature of -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is 0.

I'm not certain what to do, i believe that i've ruled out everything else. But i am afraid I may have missed something. If anyone has suggestions, please share them! 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 works on the 80,100,200, UrS, and RS2 vehicles. You can easily find a spare in a wrecking shop or parts store. It is easy to test them: simply switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing up). 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 timing of the fuel injector, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these goes badly, you will see codes on the diagnostic scanner which can lead to engine shutdown.

The signs of a failed G28 sensor are an inaccurate rev counter in the gearbox, gears shifting quicker than normal, and/or a misfire when in gear. If you experience any of these issues, it is likely that your sensor is failing and needs replacing. The good news is that they are very affordable and easily accessible particularly when you're looking at the Bosch model, like ours. Alternatively, GM's version of this part is a good option.

5. Tachometer

A damaged engine sensor could cause a number of problems in your car. It's an essential component of the transmission of your audi car key replacement since it sends information to the ECU regarding how fast or slowly the engine is spinning. If the sensor fails, it could disrupt the performance of 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. It transmits a signal to the ECU at pin T55/49, via a grey wire. The ECU is then able to process this signal to regulate the flow of fuel, timig and boost and then transmitting it to the G5 Tachometer located in the instrument cluster. You can determine if the sensor is in failure by examining the 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 [79]), and between pin T6a/1 as well as pin T26a/12. You should see a resistance of approximately 1000 ohms between these two points. This is the same across the audi key blade keyless go (pop over to these guys) 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS An and 1995 RS2 Du You may also find some good ones in wrecking yards.