The No. 1 Question Everyone Working In Audi G28 Must Know How To Answer 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. This sensor is situated on the outside of the transmission just above the flywheel gear. It sends a message to the ECU via a grey wire T55/49, then to the tachometer in the instrument cluster.


1. Engine Speed Sensor

The grey wire is situated at the edges of the transmission, just above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU then uses this information to control fuel, timig and boost. It also sends an indication to the G5 Tachometer within the instrument cluster.

The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft has reached TDC, and the position of the camshaft, so that it can activate the spark and injectors.

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 the chain stretching or a jump link on the upper chain of timing. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).

Testing can be a bit difficult since there are two connector pins and they serve different purposes however the best method of testing it is by measuring resistance between the sensor and the ECU. It should read about 1000 ohms if the sensor is operating at its maximum. Check for signs 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 full speed I noticed a massive decrease in power. It was like the engine had run out of gas. Or my injectors weren't firing. This morning i pull out the spark plugs, 3 were soaked with gazoline and the fourth was dry. audi a1 key placed a tissue over each hole in the injector and when i start the engine without sparks, the ones with gazoline jump right out. The 4th one remains closed. I checked the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ i get 0ohm. I'm assuming the issue is in another place.

I also tried to reset 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 still occurs at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of -49c even when i unplug it. Also i noticed that the gauge for oil pressure in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 if i crank up the engine.

I'm not certain what to do, i believe that i've completely ruled out all other possibilities. However, i'm afraid that I may have missed something. If anyone has any suggestions, please let me know! TIA!

3. Fuel Pump

The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style sender is identical to the 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 - 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

no title (3B AAN, ABY and ADU) engines are equipped with an ECU that needs to know the speed and position of the crankshaft to make decisions about fuel injector timing etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either one of these, the diagnostic scanner will show codes that could cause the engine shutting down.

A damaged G28 sensor could result in an inaccurate gearbox speed counter and a gearbox which shifts more quickly than normal, and/or a misfire in the gear. If you are experiencing any of these issues it is likely that your sensor is going bad and requires replacement. The good news is they are quite affordable and easily accessible particularly in the case of a Bosch sensor, like ours. Alternatively, the GM version of this part is also a great option.

5. Tachometer

A failing engine speed sensor could be the reason behind many problems in your car. It's a crucial component of the transmission of your Audi because it relays information to the ECU about how fast or slow the car's engine is turning. If this sensor fails, it could affect the performance of the transmission, as well as the rest of the car's components.

The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It sends an electrical signal through gray wire to ECU pin T55/49. The ECU then processes this signal to control the flow of fuel, timig and boost as well as transmitting it to the G5 Tachometer located in the instrument cluster. You can test the sensor for any failure by checking the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should see approximately 1000 ohms resistance between those two pins. This is the same across the Audi 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS An and 1995 RS2 Du, so you might find good ones in wrecking yards.