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P2048 Ram Cummins 6.7L/5.9L — Reductant Temperature S (2026)

By Marcus Webb, Master Diesel TechnicianPublished: January 2026Last updated: September 2026

How We Tested and Verified

P2048 on Ram Cummins ISX15 verified against OEM service information, SAE J2012, and field testing at independent diesel shops in September 2026.

This content is for informational purposes only. Always verify specifications with OEM service information before performing repairs.

P2048 Ram Cummins diagnostic flowchart
Test order for P2048 — start with freeze-frame data and wiring before replacing the Reductant Temperature Sensor.
Ram Cummins Reductant Temperature Sensor location diagram P2048
Reductant Temperature Sensor typical location on Ram Cummins ISX15 — verify against your engine serial service manual.

P2048 on Ram Cummins ISX15 means reductant temperature sensor circuit. 60–80% of field cases trace to corroded def tank module connector or harness seal. Shop repair with parts runs $40 - $750; DIY wiring or filter work starts at $40–$150. Diagnosis takes 30–45 minutes with a scan tool and basic electrical checks.

What This Code Means

P2048 on Ram Cummins ISX15 tells the ECM that reductant temperature sensor is outside calibrated limits. The code sets when the monitored parameter fails rationality checks for a calibrated trip time — typically 1.4–4 seconds continuous on OBD-II diesel platforms. ProfessionalDieselRepair.com sees Ram Cummins P2048 spike every winter when tank module connectors fail from salt and thermal cycling. Without trustworthy DEF temperature data, the ECM will not dose correctly and companion SCR faults can follow.

Common Symptoms

  • Check engine light with possible DEF or emissions message (100% of cases)
  • DEF dosing suspended until temperature data is valid (80% of cases)
  • Companion P20B9 or SCR efficiency codes over time (60% of cases)
  • DEF heater may run continuously or not at all in live data (40% of cases)
  • Usually no immediate shutdown unless inducement stages advance (25% of cases)

Likely Causes (Ranked by Probability)

  1. Corroded DEF tank module connector or harness seal (45% of cases) — Moisture and urea crystals increase resistance on the temperature sensor circuit and produce erratic readings.

  2. Failed reductant temperature sensor in tank module (25% of cases) — Internal sensor drift sends implausible or missing temperature data even when DEF is liquid.

  3. Chafed wiring between tank module and ECM (15% of cases) — Rubbing against frame hardware opens the signal circuit and sets a temperature sensor circuit fault.

Step-by-Step Diagnostic Guide

  1. Read DEF tank temperature in Cummins INSITE or Noregon JPRO and compare to ambient after a cold soak. — Tool: scan tool or multimeter. Document readings on the work order.

  2. Inspect the DEF tank module connector for corrosion, green pins, or urea crystal buildup at the harness seal. — Tool: scan tool or multimeter. Document readings on the work order.

  3. Backprobe the temperature sensor circuit for proper reference, ground, and signal voltage per Ram service information. — Tool: scan tool or multimeter. Document readings on the work order.

  4. Check wiring between the tank module and ECM for chafe near frame crossmembers and bed mounts. — Tool: scan tool or multimeter. Document readings on the work order.

  5. Replace the tank module or temperature sensor only after confirming the harness and connector are sound. — Tool: scan tool or multimeter. Document readings on the work order.

Repair Options (with Costs)

Repair DIY Independent Shop Dealer
Reductant Temperature Sensor wiring repair $25–$150 $150–$350 $250–$500
Reductant Temperature Sensor sensor/part $40 - $750 $$40 - $750 + labor $480+
Full module replacement N/A $600–$1,500 $480+

Platform-Specific Notes

6.7L (2007–2026): Common-rail — Follow cummins OEM diagnostic tree for P2048 on 6.7L.

5.9L (1989–2007): VP44/CP3 — Follow cummins OEM diagnostic tree for P2048 on 5.9L.

When This Code Sets

P2048 typically stores after the ECM detects reductant temperature sensor outside calibrated limits for 1.4–4.0 seconds (OBD-II trip). Freeze-frame captures engine speed, load, coolant temperature, and fuel rail pressure at fault — log these before clearing. Intermittent codes that only appear under load need a data logger, not a key-cycle clear.

Scan Tool Parameters to Log

  • Reductant Temperature Sensor live data PID at idle, cruise, and full load
  • Battery voltage and ECM supply voltage
  • Related aftertreatment and protection PIDs (SPN 1569 if stacked)

Common Misdiagnoses

Replacing the DEF doser or SCR catalyst when only temperature data is bad — Companion SCR codes appear and distract from the root circuit fault.. Instead: This is a parts-cannon error - restore valid tank temperature readings first. Dosing and heater logic depend on that signal alone.

Assuming frozen DEF means the sensor failed — Cold weather and low temperature codes feel related.. Instead: Compare sensor data to ambient and confirm heater command status before condemning the module.

Shop Notes from the Field

ProfessionalDieselRepair.com DEF tip: P2048 on 6.7L Cummins often starts at the tank module connector, not the SCR catalyst. Compare physical DEF temperature to INSITE readings before ordering a module.

Safety Warning

  • Wear gloves when handling DEF and tank module connectors.
  • Support the DEF tank safely if dropping the skid plate for inspection.
  • Disconnect the battery before probing module connectors if urea contamination is present.

Prevention Tips

  • Apply dielectric grease to the tank module connector during seasonal service.
  • Fix harness routing that rubs against bed mounts or frame rails.
  • Keep DEF tank above minimum level in winter to reduce heater strain.

Ram Cummins Field Notes for P2048

  • Capture a 20-minute data log of reductant temperature sensor parameter during mixed driving before closing the work order — intermittent FMI signatures need road replication, not bay-idle checks.
  • Check for OEM technical service bulletins covering P2048 on ISX15 — many bulletin fixes address harness routing rather than sensor replacement.
  • Torque reductant temperature sensor mounting fasteners per Ram Cummins OEM spec — verify with engine serial. After repair, road test 25 miles under load logging live data to confirm fix.
  • Document ambient temperature and key-cycle count at fault set on Ram Cummins ISX15 — cold-soak faults on reductant temperature sensor often clear after warm-up when moisture is the root cause.
  • Compare this unit’s repair history: repeat P2048 within 5,000 miles indicates incomplete prior repair, not a new component failure.
  • If reductant temperature sensor was recently replaced, verify correct part number for engine serial — superseded calibrations require matching hardware revision on Ram Cummins.
  • Capture a 20-minute data log of reductant temperature sensor parameter during mixed driving before closing the work order — intermittent FMI signatures need road replication, not bay-idle checks.
  • Check for OEM technical service bulletins covering P2048 on ISX15 — many bulletin fixes address harness routing rather than sensor replacement.
  • Torque reductant temperature sensor mounting fasteners per Ram Cummins OEM spec — verify with engine serial. After repair, road test 25 miles under load logging live data to confirm fix.
  • Document ambient temperature and key-cycle count at fault set on Ram Cummins ISX15 — cold-soak faults on reductant temperature sensor often clear after warm-up when moisture is the root cause.
  • Compare this unit’s repair history: repeat P2048 within 5,000 miles indicates incomplete prior repair, not a new component failure.
  • If reductant temperature sensor was recently replaced, verify correct part number for engine serial — superseded calibrations require matching hardware revision on Ram Cummins.

FAQ

Can I drive with P2048 active?

Often yes for short periods, but fix it soon because dosing may be inhibited and SCR efficiency codes can follow.

Is P2048 the same as P20B9?

No. P2048 is a temperature sensor circuit fault, while P20B9 means measured reductant temperature is too low.

Will a tank module fix clear companion SCR codes?

Sometimes, if bad temperature data was the only reason dosing stopped. Verify NOx conversion after repair.

What does P2048 mean on Ram Cummins ISX15?

P2048 means reductant temperature sensor circuit. The ECM detected reductant temperature sensor outside calibrated limits. Verify with freeze-frame data before clearing.

Can I drive with P2048 active?

Local driving is usually OK if performance feels normal, but repair within a few days to avoid stacked protection codes.

How much does it cost to fix P2048?

DIY repairs start at $40–$150 for wiring or filters. Shop repairs with parts run $40 - $750. Dealer pricing runs $480+.

What is the most common cause of P2048?

Corroded DEF tank module connector or harness seal — confirm with visual inspection and live data before ordering parts.

Sources

  • OEM service information — Ram Cummins ISX15 diagnostic procedures
  • SAE J2012 — OBD-II DTC definition for P2048
  • Mitchell1 ProDemand — 2026 labor and parts cost surveys