The Dispatch | Expert | Scudo Hub

pete12345

Member

Registered: 2025-03-09

Posts: 5

Dispatch 1.9 DCN2 Coolant Sensor Fault & Fans running constantly.

Hi all,   My brother's 2004 Dispatch has developed a fault with fans running constantly, temp gauge showing max with temp warning light & flashing Stop in the centre of the cluster.

We did diagnostics on the ECM (1.9L WJY LUCAS DCN2) & found "P0117 Coolant Temperature Signal Short Circuit To + Or Open Circuit"

• Sensor replaced with new one - no change

• Checked wiring to ECU - no shorts or broken wires

• Voltage at sensor = about 2V.   (sounds wrong)

• Cleaned all connectors with contact cleaner

After allowing engine to cool, diagnostics said 20degC.  Ran the engine, and the diagnostic temp went up to 100degC in about 3-5mins.   Checked engine with IR Thermometer, and max we could find is about 60degC.   Radiator top hose = 45degC.    Conclusion: thermostat must be opening, but max fan speed is keeping the engine cool.

My understanding is the sensor should have 5V on one side ?   Is the 5V regulator inside the ECU, or elsewhere ?

Any ideas what to check next ?

Thanks,
Pete

Last edited by pete12345 (2025-03-10 10:24:26)

pete12345

Member

Registered: 2025-03-09

Posts: 5

Re: Dispatch 1.9 DCN2 Coolant Sensor Fault & Fans running constantly.

FYI, also checked the resistance of both sensors at ambient & in boiling water.  They both go from about 6-8Kohn down to few hundred ohms in boiling water, so appear to be working & same thermal curve.

RegW

Member

From: Bristol

Registered: 2024-04-21

Posts: 334

Re: Dispatch 1.9 DCN2 Coolant Sensor Fault & Fans running constantly.

I don't have the wiring diagram for this engine but if the fans are low side switched
((ie permanent voltage to motor and relay between motor and ground)
It's possible the contacts have fused together or being held together by mechanical failure
or have a fixed 12v on the coil side due some other fault.
if i find a diagram I'll post it up.

---

When all else fails, RTFM  - 2006 Expert 2.0 HDI/110

pete12345

Member

Registered: 2025-03-09

Posts: 5

Re: Dispatch 1.9 DCN2 Coolant Sensor Fault & Fans running constantly.

Doubt it's just a fan fault.  They start at lower speed when the engine is cold.   Also I cannot see how a fan relay short would cause coolant sender faults & Stop light flashing on the dash ?

pete12345

Member

Registered: 2025-03-09

Posts: 5

Re: Dispatch 1.9 DCN2 Coolant Sensor Fault & Fans running constantly.

Hopefully to round this one off, we finally found an intermittent break in the wiring to the temperature sensor.  The problen was about halfway between the sensor & ECU, so was intermittently connecting & failing as the loom moved with the engine movement.

We then un-wrapped the loom, and replaced the two sensor wires.  The joins at each end were soldered & sleeved with heatshrink.   For last 2-3 weeks the fans, temp gauge, etc have been working ok.