How to Replace an audi a3 key fob G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. The sensor is located on the outside of the transmission just above the flywheel gear. It sends a signal to the ECU via a grey wire (T55/49) and then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The sensor is located at the edge of the transmission above the flywheel ring gear G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using a grey wire. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an alert to the G5 Tachometer within the instrument cluster.
The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and the location of the camshaft so it can activate spark and injectors accordingly.
(Image: https://g28carkeys.co.uk/wp-content/uploads/2023/10/chrome_trhg3QMQrz.png)If this sensor fails, the ECU will display the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync, possibly indicating chain stretch or a jumped link on the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40).
(Image: https://g28carkeys.co.uk/wp-content/uploads/2023/11/happy-young-woman-with-key-sitting-in-new-car-2022-12-16-21-31-14-utc-min-scaled.jpg)Testing is a bit tricky as there are two different pins for the connector and they perform different functions however the best method to test it is to measure the resistance between the sensor and the ECU. When the sensor is operational, it should be reading around 1000 ohms. Check for signs of coolant, or oil in the connector bay if you have issues with this component.
2. Injectors
Yesterday, while accelerating from the highway paytoll at maximum speed I noticed a significant drop in power. It was as if the engine was running out of gas. Or my injectors were not firing. This morning i pull out the spark plugs. Three were soaked with gazoline and the fourth was dry. When I start the engine without sparks, i place a tissue on the top of each hole in the injector and the 3 that were drenched in gazoline jump out but the 4th one stays closed. I tested the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. I'm assuming that the issue is in another location.
I also tried to reset PID but without success. The car will start when the G28 is disconnected, but it works fine when the G28 connected. However, the intermittent misfire problem persists at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows temperatures of -49c. I also noticed that the oil pressure gauge in the cockpit shows 2 bar when the actual pressure is 0.0 if i crank up the engine.
I'm not certain what to do, i feel i have pretty much eliminated everything else. But i am afraid i might have missed something. Please let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style sender is identical to the G4 and both function in the 80 100 200, UrS and RS2 cars so you can easily find one at a wrecking yard or in a local parts store. It is simple to test them - simply switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector end facing up). They should be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines requires to know the position and speed the crankshaft in order to make a decision about timing of fuel injectors, etc. To accomplish this, it uses 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 display codes that could cause 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 a misfire in gear. It is likely that your sensor is failing and needs to be replaced if you experience any of these symptoms. The good news is they are very cheap and easily accessible particularly if you're looking at the Bosch model, which is what we have. You can also choose the GM version of this part is also a good option.
5. Tachometer
A failing engine speed sensor could be the cause of a slew of problems in your car. It's a vital component of your Audi Replacement Car Keys's transmission, as it sends information to the ECU about how fast or slow the vehicle's crankshaft is spinning. If the sensor fails, it can cause problems for the transmission as well as the rest of the car's components.
The G5 engine sensor is located at the edge of the transmission, over the flywheel ring. It transmits signals via an uncolored wire to the ECU pin T55/49. The ECU is then able to process this signal to control fuel, timig and boost and then transmitting it to the G5 tachometer inside the instrument cluster. You can test 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 to pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. It should show approximately 1000 ohms resistance between those two pins. This part is common across the audi replacement key service a5 key fob (lovewiki.faith) 80-100-200-RS2 range, beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 Du, so you might find them in wrecking yards.