Background:

I fitted an AEM 30-6052 to my Australian S2K, and originally thought I had a sensor mismatch problem because my coolant temps were 60C when I was expecting 80C. I tried to solve the problem by fitting a USDM ECT sensor but there was no change in the coolant temps I was reading.

Since then, my coolant temps are now down to 50C (temps have been at 80C all along when measured using a thermometer), which corresponds to an increase of voltage at the sensor. I have now found also my TPS sensor volts are gradually increasing. 3 months ago the base TPS voltage was 0.94V , now the base TPS voltage is 1.01V. My MAP also appears to be reading higher voltage than expected but as I have changed MAP sensors recently I don't have the logging data to confirm this 100%.

Present:

Please throw any and all ideas at me which would cause high sensor voltages, that GRADUALLY INCREASE over time without anything else changing. My car audio guy has suggested a bad ground that is slowly corroding, but didn't seem convinced.

 

I think a faulty ECU ground could easily be the cause. If you measure the voltage of the sensors directly at the sensor referenced to the battery ground, does it match what the ECU sees?

 

Thanks for the input. I'm going to try and find someone who can help me do this as I don't know how to do this myself, or even own a multimeter.

 

if it was a corroding ground wouldnt you be losing volts at the sensors?

 

If you disconnect the ground completely, the voltage from the sensor will equal the voltage going in; ex. +5V or +12V. In other words, the sensor reads 100%.
So a bad ground can cause an issue in that direction.

 

I've now had a diagnostic technician look at my problem and run some tests with a multimeter. Unfortunately for me he thinks the problem is in the AEM, and it's taken me so long to diagnose it I think it's probably gone out of the warranty period.

Hopefully it can be repaired at reasonable cost and does not need to be entirely replaced.

 

EMS has now been sent back to AEM in the USA. Now I play the waiting game.

Props to AEM for giving me an RMA no hassles, even though the warranty expired in March.

 

Any time you send a product to a company for repair, they will give you an RMA number, even if it is NOT going to be repaired for free. I have an RMA number to send my FlashPro in for repair, but the repair cost will be $50 - $250 depending on what is wrong with it.

 

Ah I didn't know that, guess I'll just have to wait an see if I end up with a hefty bill or not :S

 

Update from AEM:

Issue Resolution: Bench tested and found sensor voltages unable to sweep the entire 0-5 volts range. Inspected board and found a semi-burnt resistor ground causing the declared issues. Repaired unit and fully bench tested, all sensor sweep throughout the voltage range after repairs. Customer should double check wiring again to make sure the damage does not happen again.

----------------

I'm obviously going to try and get more info from AEM on what I need to check before reconnecting the EMS but hopefully someone more knowlegeable that me can chime in. Do I need to check all grounds on the factory harness are 0V? Do I need to check all grounds on the factory harness are 5V? I'm basically just guessing with my limited knowledge of electronics.

Also, are they passing the buck a little with the "check your wiring"? Is it possible the resistor was faulty and went bad on its own? Is it possible something else inside the EMS is broken and caused the resistor to burn out?

Thanks for your input guys because in Australia I really have very limited resources to draw on for an issue like this.