DDS-3 version 8 map sensor problems

[benchmark]

Hello,

We have a system hooked up with the J link set to map for sensed pressure, but the pin 17 has a 4volt output without it being hooked up to our 2-bar map sensor. The signal wire from our sensor reads 2.1 volts at atmosphere pressure but when hooked up to pin 17 instantly goes to 4 volts both at pin 17 and at our sensor?

Any help?

Thanks
Mike

[Richard L]

Pin7 of the DDS3 has a weak pull-up resistor inducing approximately 0.1mA. Can you check the maximium current output of your MAP sensor with a DMV.

Who is the manufacturer of this MAP sensor? A typical GM MAP sensor has an output current of 25mA. If you use this sensor, the output voltage should not be affected by the DDS.

[benchmark]

It is a 2003 dodge ram 1500.. map sensor reads 4.9v maxed the pin17 reads 4.0v just by its self. If i turn the dial for the trigger to the left from maxed it will activate the pump. with or without the sensor hooked up on the junction box. why would it activate the pump just based on the dial? also if i switch the jumper from mps to pwn it reads 6.0v

[benchmark]

Ok, now the trigger wire without anything hooked up reads 10.3v which is exactly what the battery in lead reads? When hooked up to the map sensor it shows still 10.3v so is somehow feeding power thru the pin 17?

Thanks,
Mike

[Richard L]

As I said before, the weak pull up resistor will ensure for the MPS mode will trigger the system if a MAP sensor is not connected. The MAP sensor should override the default voltage induced by the 100K ohm input resistor. Have you check the output current of the MAP sensor? Almost all automotive map sensors should be able to handle an input resistance of over 50Kohms. The DDS3v8 is 100K ohms.

The DDS3 system will not work prpoperly below 12.8V. Why is you battery voltage reads 10.3V?

The DDS3v8 system has been discountinued some 3-4 years ago. it has since been superceded by v8a, v9 and v10. We still have components to service it, if you feel the DDS3v8 needs servicing, return back to us for inspection. Meanwhile attend to your low battery voltage.