20 Trailblazers Setting The Standard In Audi G28

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 located at the top of the transmission, above the flywheel ring gear. It sends a message to the ECU via a grey wire T55/49, then to the tachometer on the instrument cluster.

1. Engine Speed Sensor

It is located on the outside of the transmission just above the flywheel ring gear, the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using 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 in the instrument cluster.

The sensor is used to connect the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft has reached TDC and also the position of the camshaft, so that it can activate the spark and injectors.

If this sensor fails, the ECU will display a P00160 error message. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also be a sign of a chain stretch or a jumpy chain link in the upper chain. However the code will not appear on its own without additional information from other sensors (G4 and G40).

Testing can be a bit difficult as there are two different pins for the connector and they have different functions 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 in full operation. Look for evidence of coolant or oil in the connector bay if you are experiencing issues with this component.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at full speed, i noticed a huge decrease in power. It was as if the engine had run out of gas. Or my injectors were not firing. I took out the spark plugs this morning, 3 were soaked in gasoline, and the fourth was dry. I placed a tissue over each injector hole and when i start the engine without sparks, the ones with gazoline jump out. The 4th one remains shut. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I get 0ohm. So i assume the problem is elsewhere.

I also tried to reset the PID with no success. The car can start if the G28 is disconnected and runs fine when it is connected however it is experiencing intermittent misfires at higher RPM. The coolant sensor (G62), even when unplugged, still shows an ice temperature of -49c. Also i noticed that the gauge for oil pressure in the cockpit shows 2 bar, whereas the actual pressure is 0.0 if i crank up the engine.

I don't know what to do. I feel like i've pretty much ruled everything else out. But i'm worried that i might have missed something. Please let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter is similar to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily locate a spare in a wrecking shop or parts store. It is simple to test them: simply switch 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 in our 20vt turbo (3B AAN ABY) engines needs to know the position and speed of the crankshaft to determine timing of the fuel injector, etc. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either one of these, the diagnostic scanner will show codes that could cause an engine shut down.

A malfunctioning G28 sensor could result in an inaccurate gearbox speed counter, a gearbox that shifts more quickly than normal, and/or a misfire in gear. If you experience any of these problems, it is likely that your sensor is deteriorating and should be replaced. They're cheap and easy to find especially in the case of a Bosch sensor like ours. Alternatively, GM's version of this component is an option.

5. Tachometer

A failing engine speed sensor could be the cause of many issues in your car. It's a vital component of your audi a3 key fob replacement's transmission, as it sends information to the ECU about how fast or slow the vehicle's crankshaft is turning. This sensor could cause the transmission to malfunction and other car components to be affected.

The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It sends an electrical signal through an uncolored wire to the ECU pin T55/49. The ECU then processes the signal to control fuel, timig, and boost as well as sends it on to the G5 tachometer in the instrument cluster. You can test the sensor for any failure by checking the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. It should show approximately 1000 ohms resistance between these two points. This is a common part across the audi key fob 80, 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best ones might be availble in wrecking yards.