How to Replace an Audi G28 Engine Speed Sensor

In this video Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. The sensor is located on the outside of the transmission over the flywheel gear. It transmits a signal to the ECU via a grey wire T55/49, then to the tachometer located 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 then uses this information to control fuel, timig and boost. It also sends an indication 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 must be aware when the crankshaft is TDC and where the camshaft is so it can start spark and injectors according to the situation.

If this sensor fails, the ECU will display a P00160 code which means the Crank Shaft and Intake Camshaft aren't in sync, possibly indicating chain stretch or a jumped link on the upper chain of timing. The code won't show without the additional information supplied by other sensors (G4 or G40).

It can be a bit difficult to test as there are various connector pins, and they all have different 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. Look for signs of coolant, or oil in the connector bay if you have problems with this part.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at a high speed I noticed a significant reduction in power. It was as if the engine had run out of gas. Or my injectors were not firing. Today, i pulled out the spark plugs. Three were soaked with gazoline and the fourth was dry. When i crank the engine with no sparks, i place a tissue on top of each injector hole, the 3 drenched with gazoline jump out but the 4th stay closed. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. I get 0ohm. Therefore, i think the issue is elsewhere.

I also tried to reset the PID but without success. The car can start if the G28 is unplugged and is running fine when it is connected however it get more info has intermittent misfire issues at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows a temperature of -49c. Also, i noticed that the gauge for oil pressure in the cockpit is showing 2 bar when the actual pressure is 0.0 when i rev the engine.

I don't know what to do. I feel like i've pretty much all other possibilities out. However, i'm website afraid that I may have missed something. Please let me know If you have any suggestions! TIA!

3. Fuel Pump

The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style sender 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 junkyard or at a parts store. It is easy to test them - just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must be infinite ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY ADU) engines must know the position and speed the crankshaft to make decisions regarding timing of the fuel injector, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these sensors go wrong, you will receive codes on the diagnostic scanner which can lead to engine shutdown.

The signs of a malfunctioning G28 sensor include an inaccurate rev counter in the gearbox, gears shifting quicker than normal and/or a misfire when in gear. It is probable that the sensor is failing and requires to be replaced if you notice any of these symptoms. They're inexpensive and easy to locate particularly if they're an Bosch model like ours. Alternatively, GM's version of this part is an excellent choice.

5. Tachometer

A damaged engine sensor could cause a variety of issues within your vehicle. It's an essential component of the transmission of your Audi because it relays information to the ECU on how fast or slowly the engine of the car is spinning. 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 transmits an electrical signal through gray wire to ECU pin T55/49. The ECU uses this signal to more info regulate fuel and boost, and also to timigrate. It also relays it to the G5 Tachometer inside the instrument cluster. You can determine if the sensor is in failure by examining the continuity from the sensor to the tachometer. Also, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]) and between pin T6a/1 as well as pin T26a/12. You website should detect a resistance of approximately 1000 ohms between these two points. This part is common across the Audi 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS AN website and the 1995 RS2 Du, so you might find good ones in wrecking yards.