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DTC codes / Chrysler codes / P1188

P1188 · ChryslerEOT Sensor Circuit High Voltage

P1188 on Chrysler vehicles indicates the Engine Oil Temperature (EOT) sensor circuit is reporting a voltage higher than the normal operating range, which the Powertrain Control Module (PCM) interprets as an open circuit or sensor signal wire shorted to voltage. The PCM expects the EOT sensor to produce a voltage between roughly 0.5 and 4.5 volts as oil temperature changes, and a sustained high reading sets this code.

SystemPowertrain
Code typeChrysler specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering

Symptoms you may notice

  • Illumination of the Check Engine Light (MIL) with no other noticeable drivability issues
  • Oil temperature gauge or dashboard display reading abnormally low or not moving
  • Poor fuel economy or slightly rough running when the engine is cold, because the PCM substitutes a default oil temperature value
  • In rare cases, a no-start condition or extended cranking if the PCM misjudges oil viscosity for fuel injection timing
  • Intermittent warning light that comes and goes with vibration or temperature changes

Common causes, most likely first

  1. Failed Engine Oil Temperature (EOT) sensor, typically an open internal thermistor
  2. Damaged or disconnected electrical connector at the EOT sensor
  3. Open circuit in the signal wire between the EOT sensor and the PCM
  4. Short to voltage on the EOT signal wire, often from chafed insulation against a hot engine component
  5. Corroded or pushed-back terminals in the EOT sensor harness connector
  6. Faulty Powertrain Control Module (PCM) internal pull-up resistor or processing circuit, though this is rare

How to diagnose and fix it

  1. Connect a scan tool and read live data for Engine Oil Temperature (EOT) to confirm the sensor voltage is stuck high and compare it to a cold-engine baseline
  2. Visually inspect the EOT sensor connector and harness for loose pins, corrosion, or obvious wire damage, and repair as needed
  3. Disconnect the EOT sensor and measure resistance across its terminals with a multimeter, comparing to the manufacturer's temperature-resistance chart
  4. With the sensor disconnected and the key on, measure voltage on the signal wire at the sensor connector to check for a short to voltage or an open circuit
  5. Perform a wiggle test on the harness while watching live EOT data to expose intermittent opens or shorts
  6. If the circuit checks out, substitute a known-good EOT sensor and clear the code to see if it returns
  7. As a last step, diagnose the PCM by checking reference voltage and ground integrity at the PCM connector before condemning the module

What a high EOT voltage really tells you

  • A high voltage reading on the EOT circuit almost always means the PCM is seeing an open circuit, not necessarily a failed sensor, so inspect the wiring and connector before replacing parts.
  • Chrysler EOT sensors share a reference voltage and ground with other engine sensors on some models, so a fault in a shared circuit can set P1188 alongside other sensor codes.
  • The PCM may default to a fixed oil temperature value when this code is active, which can affect fuel injection timing and variable valve timing on engines that use oil temperature for those calculations.
  • After an engine replacement or major service, the EOT sensor connector is easily left unplugged or damaged, causing this code to appear immediately after the repair.
  • Do not confuse this code with P1189 (EOT sensor circuit low voltage); the diagnostic path is opposite, so confirm the code number before testing.

Can I keep driving with P1188?

You can generally drive the vehicle with P1188 because the PCM substitutes a default oil temperature, but avoid heavy towing or sustained high-speed driving until the fault is repaired, since the engine may not protect itself correctly if oil temperature actually rises.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Chrysler vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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