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 near the transmission's edge over the flywheel gear. It sends a signal to the ECU via an uncolored wire (T55/49) which is then sent to the tachometer located 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 an electrical signal to ECU pin T55/49 via the grey wire. The ECU utilizes this information to control fuel and boost. It also sends an indicator to the G5 Tachometer located in the instrument cluster.
The sensor is used to link with the G40 Camshaft position Sensor. The ecu must be aware of when the crankshaft has reached TDC and also the position of the camshaft, to trigger the spark and injectors.
If this sensor fails the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft are out of sync, possibly indicating chain stretch or a jumped 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).
It's a bit tricky to test as there are various pins on the connector and each has its own functions. The best method for doing this is to measure the resistance between the ECU and the sensor. When the sensor is operational, it should read approximately 1000 ohms. If you're experiencing issues with this sensor, look for evidence of oil or coolant in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at full speed I noticed a significant drop in power. It was like the engine was running out of gas. Or my injectors weren't firing. I pulled out the spark plugs this morning and found that 3 were soaked with gasoline and the fourth was dry. I put a piece of tissue over each injector hole and when I start the engine without sparks, the 3 that have gazoline pop right out. The fourth one remains closed. I tested the ground connection on ECU pins 14/55,30/55 and 48/55 I got zero ohm. I think the issue is in another location.
I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it runs fine with the G28 plugged in. However the intermittent misfire issue still occurs at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is zero.
I'm not sure what to do. I feel like i've pretty much eliminated everything else. But i'm worried that i might 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 transmitter functions similarly to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily find an extra in a wrecking shop or parts store. It is simple to test them - just put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They should be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines needs to know the speed and position of the crankshaft to make decisions regarding timing of the fuel injector, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these go bad you will get codes on the diagnostic scanner which can lead to engine shutdown.
A failing G28 sensor could result in an inaccurate speed counter for your gearbox, a gearbox that shifts more quickly than normal, and/or an unfire when in the gear. It is likely that the sensor is failing and needs to be replaced if you experience any of these symptoms. They are cheap and easy-to-find, especially if they're an Bosch sensor like ours. Alternatively, the GM version of this part is also a good option.
5. Tachometer
A failing engine speed sensor could be a cause for numerous issues with your vehicle. It's a vital component of your Audi's transmission, as it sends information to the ECU about how fast or slow the vehicle's crankshaft is turning. When this sensor fails, it can disrupt the performance of the transmission and the rest of the car's components.
The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It sends a signal via an uncolored wire to the ECU pin T55/49. The ECU is then able to process this signal to control the flow of 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 to pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see around 1000 ohms of resistance between those two pins. This part is common across the Audi 80-100-200-RS2 model, ranging beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 Du So, you may find them in wrecking yards.