How to Replace an Audi G28 Engine Speed Sensor

In this video Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is situated on the edge of the transmission above the flywheel ring gear. It transmits a signal the ECU via a grey wire (T55/49), then to the tachometer in the instrument cluster.

1. Engine Speed Sensor

It is located on the outside of the transmission, above the flywheel ring gear, the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through an uncolored wire. The ECU then uses this information to control fuel, timig and boost. It also sends signals to the G5 tachometer inside 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 the location of the camshaft so it can start spark and injectors in the right way.

If this sensor fails to function, the ECU will display a P00160 error code. This indicates that the Crank Shaft is not in sync 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. However, the code won't appear on its own without additional information from other sensors (G4 and G40).

Testing is a bit challenging because there are two pins for the connector and they serve different purposes but the best method of testing it is by measuring resistance between the sensor and the ECU. It should read approximately 1000 ohms when it is in full operation. If you are having problems with this component, look for evidence of oil or coolant in the connector bay.

2. Injectors

Yesterday, while accelerating from the highway paytoll at maximum speed, i noticed a huge decrease in power. It was as if the engine was running out of gas. Or my injectors were not firing. I pulled out the spark plugs this morning, three were soaked in gasoline, and the fourth was unclean. I put tissue over each injector hole and when i turn the engine on without sparks, the three with gazoline jump out. The fourth one remains shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I got 0ohm. I'm assuming that the issue is in another location.

I also tried to reset the PID with no success. The car will start when the G28 is not plugged in and it runs perfectly when it is plugged in, but still has intermittent misfire issues at higher RPM. The coolant audi car keys sensor (G62) even when unplugged, still shows an ice temperature of -49c. I also noticed that the oil pressure gauge 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 believe that I've all other possibilities out. I'm concerned that i may have missed something. If anyone has any suggestions, please chime in! TIA!

3. Fuel read more Pump

The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style transmitter is the same as the website G4 and both are used 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 simple to test them - simply audi replacement car keys 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

Our 20vt turbo (3B AAN, ABY, and ADU) engines are equipped with an ECU that needs to know the speed and position of the crankshaft in order to make decisions regarding timing of the fuel injectors, etc. It makes use of 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.

Some of the signs of a failed G28 sensor include an inaccurate rev counter in the gearbox, gears shifting quicker than normal and/or a misfire when you are in gear. It is likely that your sensor is failing and needs to be replaced if you experience any of these signs. They are cheap and easy-to-find, especially in the case of an Bosch model like ours. If you prefer, GM's version of this part would be an excellent choice.

5. Tachometer

A failing engine sensor could cause a myriad of issues within your vehicle. It's a vital component of your Audi's transmission, as it sends information to the ECU about how fast or slow the vehicle's crankshaft is rotating. If this sensor fails, it can cause problems for the transmission as well as the rest of the car's components.

The G5 engine speed sensor is located at the outside of the transmission above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 via an uncolored wire. The ECU is then able to process the signal to control the flow of fuel, timig and boost as well as transmitting it to the G5 tachometer in the instrument cluster. You can check the sensor for failure by examining the 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 T6a/1 and the instrument cluster pin T26a/12. You should see approximately 1000 ohms resistance between these two points. This is a common part that is found across the Audi 80 100 200, UrS read more and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU. Good ones might be availble in wrecking yards.