7 Small Changes That Will Make An Enormous Difference To Your Audi G28

How to Replace an Audi Q7 key G28 Engine Speed Sensor

In this video Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is situated at the edge of transmission over the flywheel gear. It sends a signal to the ECU via an uncolored wire (T55/49), then to the tachometer within the instrument cluster.

1. Engine Speed Sensor

The grey wire is located on the edge of transmission, above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends an indicator to the G5 Tachometer located in the instrument cluster.

The sensor serves as a reference point to connect 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 the ECU will throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync, possibly indicating chain stretch or a jumped link on the upper timing chain. However, the code won't be displayed on its own without additional information from other sensors (G4 and G40).

Testing is a bit challenging because there are two connector pins and they serve different purposes however the best method to test it is by measuring resistance between the sensor and the ECU. It should read about 1000 ohms if the sensor is in full operation. Look for signs of coolant or oil in the connector bay if you are experiencing issues with this part.

2. Injectors

Yesterday, when accelerating from highway paytoll at maximum speed I noticed a massive drop 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. Three were drenched with gazoline the 4th one was dry. When I start the engine without sparks, i place a tissue on the top of each of the injector holes and the 3 that were drenched in gazoline leap out, however the 4th stay closed. I inspected the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I get zero Ohm. So i assume the problem is somewhere else.

I also tried to reset the PID without success. The car will start when the G28 is disconnected, but it is running fine with the G28 connected. However the intermittent misfire issue persists at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature of -49c even when i unplug it. Also, i noticed that the oil pressure gauge in the cockpit is showing 2 bar when the actual pressure is 0.0 if i crank up the engine.

I'm not sure what to do, but i think i've pretty much completely ruled out all other possibilities. I'm afraid i may have missed something. If anyone has suggestions, please share them! TIA!

3. Fuel Pump

The fuel pump in the g28 receives signals from 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 locate a spare in a wrecking shop or 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 up). They should be infinite Ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that must be aware of the speed and position of the crankshaft in order to make decisions regarding timing of the fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these goes wrong, you will receive codes on the diagnostic scanner which can cause the engine to shut down.

A damaged G28 sensor can cause an inaccurate speed counter for your gearbox, a gearbox that shifts faster than normal, and/or an unfire when in the gear. If you have any of these issues, it is likely your sensor is deteriorating and needs replacing. The good news is they are very cheap and readily available particularly in the case of an Bosch sensor, which is what we have. Alternately, GM's version this component is a good option.

5. Tachometer

A malfunctioning engine sensor can cause a variety of issues in your vehicle. It is an important part of the transmission in your audi a1 key since it sends information to the ECU on how fast or slowly the engine of the car is turning. This sensor could cause the transmission to fail and other car components to be affected.

The G5 engine speed sensor is located on the edge of the transmission, above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49, via an uncolored wire. The ECU then uses and processes this signal to regulate fuel, timig and boost, and also sends it on to the G5 tachometer in the instrument cluster. You can test the sensor replacement key for audi failure by examining the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should observe approximately 1000 ohms resistance between these two points. This part is common across the audi connect key 80-100-200-RS2 range, from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 DU So, you may find good ones in wrecking yards.