OEM Pressure/Temperature Switch Input Short Circuit
What does CUMMINS-1321 mean?
The CUMMINS-1321 (Cummins) diesel fault code means: OEM Pressure/Temperature Switch Input Short Circuit. This is a low severity code.
Common Symptoms
- Check Engine Light illuminated
- Sensor-related gauge reads zero or max
- Possible engine derate
- Fault code active on scan tool
- May affect cold start performance
Probable Causes (Ranked by Likelihood)
- Failed sensor element Very Likely
- Open or shorted wiring to sensor Likely
- Corroded or backed-out connector pin Likely
- 5V reference supply out of spec Possible
- ECM input circuit fault Less Likely
Step-by-Step Diagnostic Procedure
Connect INSITE and monitor the sensor live data associated with SPN 697 -- compare against known-good spec.
Unplug sensor connector and inspect for bent, corroded, or backed-out pins. Check for moisture intrusion.
Measure 5V reference at signal return line (should be 4.9-5.1V key-on with sensor unplugged).
Measure sensor resistance across signal and return pins per Cummins service manual spec.
Backprobe harness and wiggle-test while watching live data for intermittent faults.
If sensor tests in-spec, inspect harness between sensor and ECM for chafing or pinches.
Frequently Asked Questions
What is Cummins fault code 1321?
Cummins fault code 1321 indicates: OEM Pressure/Temperature Switch Input Short Circuit. It is a low-severity fault affecting a specific engine or aftertreatment sensor.
Can I drive with Cummins fault code 1321?
Yes, short-term driving is typically safe with fault 1321, but the fault will illuminate the Check Engine Light and must be diagnosed soon. Monitor for power loss, unusual noises, or gauge changes and pull over if conditions worsen.
How much does it cost to fix Cummins fault 1321?
Repair cost is approximately $150-$500 including parts, labor, and any dealer programming required. DIY repairs (sensor replacement) fall at the low end; pump, aftertreatment, or ECM work falls at the high end and usually requires INSITE diagnostic software.