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 at the top of the transmission, above the flywheel ring gear. It transmits a signal to the ECU via the grey wire (T55/49), then to the tachometer within the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the edge of transmission, directly above the flywheel ring. This sensor sends a signal via the grey wire to pin T55/49. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an indicator to the G5 Tachometer in instrument cluster.
The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and the location of the camshaft so it can trigger spark and injectors in the right way.
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 the chain stretching or a jump link on the upper timing chain. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).
Testing is a bit challenging as there are two different connector pins, and they have different functions but the most effective way to test it is to measure the resistance between the sensor and the ECU. If the sensor is operational, it should be reading approximately 1000 ohms. 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 a high speed I noticed a massive reduction in power. It was like the engine had run out of gas. Or, my injectors were not firing. In the morning, i removed the spark plugs, 3 were soaked with gazoline and the 4th one was dry. I placed a tissue over each injector hole, and when i turn the engine on without sparks, the ones that have gazoline pop right out. The 4th one remains closed. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I get zero ohm. I'm assuming the issue is somewhere else.
I also tried to reset the PID but with no luck. The car can start when the G28 is disconnected and it runs perfectly when it is connected, but still has intermittent misfire issues at higher RPM. audi a1 key G28 Car Keys (G62), even if it is not plugged in, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is 0.
I'm not certain what to do, as i think i've pretty much completely ruled out all other possibilities. But i am afraid I may have missed something. Let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style transmitter is identical to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or a parts store. It is easy to test them: simply switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to be aware of the speed and position of the crankshaft to determine timing of the fuel injector, etc. In order to do this it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these, the diagnostic scanner will display codes that could lead to an engine shut down.
A malfunctioning G28 sensor could cause an inaccurate speed counter for the gearbox and a gearbox which shifts more quickly than normal, and/or an unfire when in gear. It is probable that your sensor is failing and requires to be replaced if you encounter any of these symptoms. They're inexpensive and easy to locate, especially when they're a Bosch sensor like ours. If you prefer, GM's version of this part is an excellent choice.
5. Tachometer
A malfunctioning engine speed sensor could be the reason behind many issues with your car. It's an essential component of your Audi's transmission, because it communicates to the ECU about how fast or slow the car's crankshaft is spinning. This sensor could cause the transmission to malfunction and other components in the car to be affected.
The G5 engine speed sensor is located on the outside of the transmission, above the flywheel ring gear and sends a signal directly 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 sends it on to the G5 Tachometer located in the instrument cluster. You can test for sensor failure by examining the continuity from the sensor to the tachometer. You can also 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 and pin T26a/12. You should detect a resistance of approximately 1000 ohms in these areas. This is a typical part across the Audi 80, 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.