MediumISX15

P0117 Ram Cummins 6.7L/5.9L — Coolant Temp Fault (2026)

P0117 on Ram Cummins ISX15 means engine coolant temperature circuit low input. 60–80% of field cases trace to signal wire shorted to a grounded engine surface. Shop repair with parts runs $25 - $150; 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

P0117 on Ram Cummins ISX15 tells the ECM that engine coolant 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. This is a genuine electrical short, distinct from the plausibility-based P0116 code. ProfessionalDieselRepair.com always traces the signal wire for contact with a grounded surface near the engine block first, since that’s a more common cause than an actually failed sensor.

Common Symptoms

• Check engine light with cooling fan possibly running constantly (100% of cases)
• Poor heater output since the ECM thinks the engine is already hot (80% of cases)
• Possible rich-running condition affecting fuel economy (60% of cases)
• No major drivability complaint in most cases (40% of cases)

Likely Causes (Ranked by Probability)

1. Signal wire shorted to a grounded engine surface (45% of cases) — A chafed wire contacting the engine block or another grounded component pulls the signal voltage down to near zero.

2. Internally shorted sensor (25% of cases) — A sensor with an internal short can present the same low-voltage signature as a wiring fault.

3. Corroded connector causing a partial short (15% of cases) — Moisture intrusion at the connector can create a path to ground that produces a similar low-reading fault.

Step-by-Step Diagnostic Guide

1. Pull the fault and freeze-frame coolant temperature data with Cummins INSITE - a value pinned at an unrealistic low reading confirms the short-to-ground condition. — Tool: scan tool or multimeter. Document readings on the work order.

2. Locate the coolant temperature sensor and unplug the connector. — Tool: scan tool or multimeter. Document readings on the work order.

3. Back-probe signal and ground with a multimeter, key on engine off - a reading near 0V with the sensor disconnected confirms a harness-side short to ground. — Tool: scan tool or multimeter. Document readings on the work order.

4. Trace the signal wire for chafing against the engine block, exhaust manifold, or other grounded surfaces. — Tool: scan tool or multimeter. Document readings on the work order.

5. Test sensor resistance at the connector against the OEM temperature/resistance chart to rule out an internally shorted sensor. — Tool: scan tool or multimeter. Document readings on the work order.

6. Repair the wiring or replace the sensor as needed, then clear the code and confirm a plausible reading returns. — Tool: scan tool or multimeter. Document readings on the work order.

Repair Options (with Costs)

Repair	DIY	Independent Shop	Dealer
Engine Coolant Temperature Sensor wiring repair	$25–$150	$150–$350	$250–$500
Engine Coolant Temperature Sensor sensor/part	$25 - $150	$$25 - $150 + labor	$260+
Full module replacement	N/A	$600–$1,500	$260+

Platform-Specific Notes

6.7L (2007–2026): Common-rail — Follow cummins OEM diagnostic tree for P0117 on 6.7L.

5.9L (1989–2007): VP44/CP3 — Follow cummins OEM diagnostic tree for P0117 on 5.9L.

When This Code Sets

P0117 typically stores after the ECM detects engine coolant 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

• Engine Coolant 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 sensor without pin-testing the harness — The sensor is a fast parts-cannon swap that skips the cheaper wiring inspection.. Instead: Back-probe the harness with the sensor disconnected - a reading still near 0V confirms the fault is in the wiring, not the sensor.

Shop Notes from the Field

Shop tip: ProfessionalDieselRepair.com always pin-tests this circuit before replacing the sensor - a wire shorted to a grounded surface near the engine block is a more common cause than an actually failed sensor element.

Safety Warning

• Allow the engine to cool before accessing the coolant temperature sensor near the engine block.
• Disconnect the battery before repairing any chafed wiring.

Prevention Tips

• Route and secure wiring away from the engine block and other grounded surfaces.
• Inspect connector pins for corrosion during routine PM services.
• Address any minor sensor circuit warnings promptly before they progress.

Ram Cummins Field Notes for P0117

• Check for OEM technical service bulletins covering P0117 on ISX15 — many bulletin fixes address harness routing rather than sensor replacement.
• Torque engine coolant 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 engine coolant temperature sensor often clear after warm-up when moisture is the root cause.
• Compare this unit’s repair history: repeat P0117 within 5,000 miles indicates incomplete prior repair, not a new component failure.
• If engine coolant 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 engine coolant 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 P0117 on ISX15 — many bulletin fixes address harness routing rather than sensor replacement.
• Torque engine coolant 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 engine coolant temperature sensor often clear after warm-up when moisture is the root cause.
• Compare this unit’s repair history: repeat P0117 within 5,000 miles indicates incomplete prior repair, not a new component failure.
• If engine coolant 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 engine coolant temperature sensor parameter during mixed driving before closing the work order — intermittent FMI signatures need road replication, not bay-idle checks.

Related Codes

• P0118 — often stacks with P0117
• P0116 — often stacks with P0117

FAQ

Can I drive with this code active?

Yes, this code doesn’t trigger a derate or shutdown, though you may notice the cooling fan running more than usual and reduced heater output.

How do I reset this code without a scanner?

Use Cummins INSITE or Diesel Laptops to clear the code once the wiring or sensor repair is verified.

Why does the ECM think my engine is hot when it’s not?

A short-to-ground pulls the sensor voltage down, which the ECM interprets as an implausibly high coolant temperature reading.

What does P0117 mean on Ram Cummins ISX15?

P0117 means engine coolant temperature circuit low input. The ECM detected engine coolant temperature sensor outside calibrated limits. Verify with freeze-frame data before clearing.

Can I drive with P0117 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 P0117?

DIY repairs start at $40–$150 for wiring or filters. Shop repairs with parts run $25 - $150. Dealer pricing runs $260+.

What is the most common cause of P0117?

Signal wire shorted to a grounded engine surface — 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 P0117
• Mitchell1 ProDemand — 2026 labor and parts cost surveys

Related Reading

• Ram Cummins fault codes hub
• Diesel repair cost estimator
• Engine Coolant Temperature Sensor diagnostic guide
• P0118
• P0116