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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. This sensor is situated at the edge of transmission just above the flywheel gear. It sends a message to the ECU through the grey wire T55/49 and 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 signals to ECU pin T55/49 through an uncolored wire. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends signals to the G5 tachometer inside the instrument cluster.

The sensor is used to connect with the G40 Camshaft position Sensor. The ecu has to know when the crankshaft reached TDC, and where the camshaft lies in order to activate the spark and injectors.

If this sensor fails, the ECU will throw 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 will not appear without the additional information supplied by other sensors (G4 or G40).

It can be a bit difficult to test since there are different 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 approximately 1000 ohms when it is in full operation. Check for evidence of coolant or oil in the connector bay if there are issues with this part.

2. Injectors

Yesterday, while accelerating from the highway paytoll at full speed, i noticed a huge drop in power. It was like the engine had run out of gas. Or, my injectors weren't firing. In the morning, i removed the spark plugs. Three were drenched with gazoline the 4th one was dry. I placed a tissue over each hole in the injector and when i turn the engine on without sparks, the 3 with gazoline jump right out. The 4th one stays shut. I inspected the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got zero ohm. I'm assuming that the issue is in another location.

I also tried to 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 the intermittent misfire issue at higher RPM. The coolant sensor (G62), even when it is unplugged, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is zero.

I'm not sure what to do, as i think i've pretty much ruled out everything else. However, i'm afraid that i might have missed something. If anyone has any ideas please let me know! 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 functions similarly to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily locate an extra in a wrecking shop or a parts store. It is simple to test them: simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing up). They must be infinite Ohms.

4. ECU

The ECU of our read more 20vt turbo (3B AAN ABY) engines needs to be aware of the position and speed of the crankshaft to make decisions regarding fuel injector timing, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you encounter a problem with either one of these, the diagnostic scanner will show codes that could lead to an engine shutdown.

A malfunctioning G28 sensor could cause an inaccurate speed counter for your gearbox and a gearbox which shifts more quickly than normal, or a misfire in the gear. If you are experiencing any of these issues, it is most likely that your sensor is deteriorating and should be replaced. The good news is they are very cheap and easy to find, especially in the case of the Bosch sensor, which is what we have. Alternatively, GM's version of this part would be an excellent choice.

5. Tachometer

A malfunctioning engine speed sensor could be the cause of numerous issues in your car. It's an essential component of your Audi's transmission, as it sends information to the ECU about how the car's crankshaft is turning. This sensor could cause the transmission to malfunction and other car components to be affected.

The G5 engine speed sensor is located at the outside of the transmission, above the flywheel ring gear. It transmits a signal to get more info the ECU at pin T55/49 through a grey wire. The ECU then uses and processes this signal to regulate fuel, timig, and boost and then sends it on to the G5 tachometer inside the instrument cluster. You can check for sensor failure by examining the continuity from the sensor to the tachometer. here Also, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]), and between pin T6a/1 as well as pin T26a/12. It should show approximately click here 1000 ohms resistance 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 and the 1995 RS2 Du, so check here you might find them in wrecking yards.