How to Replace an Audi G28 Engine Speed Sensor

Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. This sensor is located near the transmission's edge just above the flywheel gear. It transmits a signal to the ECU through a grey wire T55/49, then to the tachometer on the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission above the flywheel ring gear the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 via a grey wire. The ECU uses this information to regulate the amount of fuel and boost. It also sends a signal to the G5 tachometer in the instrument cluster.

The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu needs to be aware of when the crankshaft has 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 sync with the Intake Camshaft. It could also be a sign of a chain stretch or a jumpy chain link in the upper chain of timing. However the code will not be displayed on its own without additional information from other sensors (G4 and G40).

It's a bit tricky to test since there are various pins on the connector and each has its own functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. It should read around 1000 ohms if the sensor is at full operation. Check for evidence of coolant or oil in the connector bay if there are issues with this part.

2. Injectors

Yesterday, when accelerating from highway paytoll at a high speed I noticed a significant reduction in power. It was like the engine had run out of gas. Or my injectors weren't firing. I took out the spark plugs this morning and found that 3 were soaked with gasoline and the 4th was dry. I put a piece of tissue over each injector hole and when i turn the engine on without sparks, the 3 with gazoline jump out. The fourth one remains closed. I checked the ground connection of ECU pins 14,30, and 48/55. I got 0ohm. I'm assuming the issue is elsewhere.

I also tried to car key replacement audi reset PID without success. The car is able to start when the G28 is disconnected and it runs perfectly when it is plugged in, but still has intermittent misfire issues at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is zero.

I'm not more info sure what to do, but i feel i have pretty much completely ruled out all other possibilities. But i'm worried that i might have missed something. If anyone has any ideas 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 transmitter is the same as the G4 and they both work in the 80, 100 200, UrS and RS2 cars so you can easily find one at a salvage yard or in a local parts store. It is simple to test them - just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that must know the position and speed of the crankshaft in order to make a decision about fuel injector timing etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these go badly, you will see codes on the diagnostic scanner which can lead to engine shutdown.

A failing G28 sensor could result in an inaccurate gearbox speed counter or a gearbox that shifts faster than normal, or an unfire when in the gear. If you are experiencing any of these issues it is likely your sensor is going bad and should be replaced. They're cheap and easy to find especially in the case of an Bosch sensor like ours. Alternatively, GM's version of this part is an excellent choice.

5. Tachometer

A failing engine sensor could cause a myriad of issues within check here your vehicle. It's an essential component of the transmission in your Audi, as it transmits information to the ECU on how fast or slow the engine is turning. If the sensor fails, it can affect 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 transmission, above the flywheel ring. It sends an electrical signal through an uncolored wire to the ECU pin T55/49. The ECU utilizes this signal to regulate the flow of fuel and boost as well as timig. It also sends it to the G5 Tachometer in instrument cluster. audi a1 key replacement You can test the sensor for failure by checking continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79trace [79]) and between pin audi replacement key T6a/1 and the instrument cluster pin T26a/12. You should see around 1000 ohms of resistance between those points. This is a common part that is found across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.