How To Troubleshoot P0117 And P0118 -ECT Sensor Tests (1996-2003 5.2L, 5.9L V8 Dodge Ram Pickup)

By: Abraham Torres-Arredondo
Created: 20 May 2025
Updated: 22 May 2025
Articl Id: 1711

Page 3 of 3

TEST 6: Checking For Shorts Between ECT Wires Or To Ground

Checking For Shorts Between ECT Wires Or To Ground. How To Troubleshoot P0117 And P0118 -ECT Sensor Tests (1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003 5.2L, 5.9L V8 Dodge Ram Pickup)

This test will help determine whether code P0117 or P0118 is being triggered by one of two common types of short-circuit issues:

A short between the ECT sensor's two wires.
A short to Ground affecting either wire individually.

These types of electrical faults usually happen when the insulation on one of the ECT sensor wires gets damaged, exposing the copper underneath.

If the bare copper strands from the two ECT sensor wires touch each other, it creates a short-circuit between them. If they come into contact with the engine or chassis metal, you'll get a short to Ground.

These issues often occur inside the wiring harness, where the damage isn't visible —so we really can't rely on a visual inspection alone.

We'll begin by checking for continuity between the two wires at the ECT sensor's plug. These should be completely separate and must not show any connection to each other.

Next, we'll test each wire for continuity to Ground, which would indicate that one of them is unintentionally contacting the engine block or vehicle frame.

IMPORTANT: Before running these checks, make sure all three PCM connectors are disconnected. Leaving them connected can interfere with your results and cause misleading readings.

OK, these are the test steps:

PART 1: Check If ECT Sensor Wires Are Shorted Together

1
Make sure the battery negative (-) cable is disconnected from its battery post.
2
Double-check the PCM is disconnected from its 60 pin connector.
3
Set your multimeter to continuity or Ohms (Ω) mode.
4
Probe both female terminals of the ECT sensor connector.
5
The multimeter should show no continuity (infinite resistance or no beep).

Any continuity between these two wires indicates a short between them inside the wiring harness.

PART 2: Check If Either ECT Wire Is Shorted to Ground

1
Keep your multimeter in continuity or Ohms (Ω) mode.
2
Place one multimeter lead on one terminal of the ECT sensor connector.
3
Place the other lead on the battery negative cable (still disconnected from the battery post).
4
Repeat for the second wire.
5
There should be no continuity in either test.

If the meter beeps or shows a low resistance value, that wire is shorted to Ground.

Now let's go over how to interpret your results:

CASE 1: No continuity between the wires, and no continuity to Ground. This is exactly what you want to see. It confirms there are no shorts in the wiring —both circuits are isolated and functioning as they should.

If you're still missing the 5V ECT (+) signal, there's a chance the PCM's internal ECT circuit is faulty. More info here: What If The PCM Itself Is Bad?

If the Ground circuit tests good for continuity but still isn't providing a solid Ground, disconnect any sensors or modules that also connect to the BLK/LT BLU wire. Then repeat the test to eliminate possible interference or voltage feedback. See: Watch Out For Shared Sensor Ground Circuits.

CASE 2: Continuity detected between the two wires. This confirms the ECT (+) signal and ECT (-) wires are contacting each other somewhere inside the engine wiring harness.

You'll need to fix this short. These two guides can help walk you through the repair process:

CASE 3: One or both wires are shorted to Ground. This means that the internal copper strands of the wire (showing continuity to Ground) is making contact with metal parts of the engine —usually due to damage or a failure in the wire's insulation.

The resources below will help you to fix this type of issue:

What If The PCM Itself Is Bad?

If you've made it this far, you've put in the work. You've run all the essential tests, double-checked your findings, and maybe even installed a brand-new ECT sensor that tested good on the bench.

So what happens if everything looks solid, yet the check engine light keeps coming back with an ECT-related code?

Although it's very uncommon, a failure inside the PCM —specifically the portion of the circuit that processes the ECT signal —can be the culprit.

However, before considering PCM replacement, you need to be absolutely sure you've ruled out every other possibility:

Verified that the 5-Volt reference and Ground are both missing at the ECT connector (see TEST 1).
Confirmed the sensor's resistance aligns with ambient temperature readings (see TEST 2).
Checked that the ECT signal reaching the PCM is stable and doesn't drop out (see TEST 3).
Tested for full continuity from the ECT connector to the PCM on both wires (see TEST 4).
Ruled out shorts between the wires or to chassis Ground (see TEST 5).
Replaced the sensor with a known-good or new one just to be sure.
Checked that no other component using the same Ground (BLK/LT BLU wire) is backfeeding voltage or causing interference (refer to: Watch Out For Shared Sensor Ground Circuits).

If all of the above checks have been completed and passed, then —and only then— should the PCM itself be considered suspect.

Remember, the PCM is always the last suspect —never the first. Always eliminate all basic causes before assuming a computer failure.

Watch Out For Shared Sensor Ground Circuits

One problem I've run into repeatedly over the years wrenching on cars, is something that can throw off your test results without warning: shared sensor Ground circuits.

The black with light blue stripe (BLK/LT BLU) wire provides Ground for the ECT sensor and is supplied straight from the PCM.

But here's where things get tricky: that same Ground wire is also shared by several other critical sensors, including:

Battery temp sensor.
Camshaft Position (CMP) sensor.
Crankshaft Position (CKP) sensor.
Engine oil pressure sensor.
Throttle Position Sensor (TPS).
Intake Air Temperature (IAT) sensor.
Vehicle Speed Sensor (VSS).
Oxygen (O2) sensors.
Manifold Absolute Pressure (MAP) sensor.
Transmission solenoid assembly.

The exact sensors on that shared Ground circuit may vary by model and year. To be sure, consult your vehicle's wiring diagram and follow the BLK/LT BLU wire throughout the circuit. This will show you how many components share the Ground and help you identify where an issue might be originating.

Why this matters: If any sensor tied into that Ground develops an internal fault —especially a short to power— it can disrupt the entire Ground path. This can cause multiple sensors to stop working properly or deliver incorrect readings, even if they're functioning normally.

In fact, what may appear to be an ECT sensor issue could actually be caused by a completely different sensor feeding voltage back into the shared Ground wire —confusing the PCM and affecting all sensors on the circuit.

I've seen this happen quite a few times —a single faulty sensor contaminated the Ground path with voltage, throwing off the PCM's readings across the board.

PRO TIP: If your voltage or continuity results on the Ground circuit seem off, try unplugging the other sensors that share the BLK/LT BLU wire and running the test again.

This step can help isolate a sneaky sensor that's backfeeding voltage and prevent you from misdiagnosing a good ECT sensor or even replacing a PCM unnecessarily.

If, after disconnecting all shared sensors, you're still seeing the same issue, you've ruled out sensor interference —the problem is likely in the wiring or within the PCM itself.

Don't let this trip you up —it's well within your ability to fix. Just grab the wiring diagram, trace the Ground path, and test by unplugging sensors one at a time if needed. This method can save you hours of unnecessary troubleshooting and costly parts replacement.

More 5.2L, 5.9L V8 Dodge Ram Pickup Tutorials

I've written several more tutorials for the V8 Dodge Ram pickups that may be of interest to you that you can find in this index:

5.2L, 5.9L V8 Dodge Ram Pickup Index Of Articles.

Here's a sample of the tutorials you'll find in the index:

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