TEST 3: Checking The 3-4 Shift Solenoid Control Circuit For A Short To Ground
The brown (BRN) wire running from pin 21 of the WHITE PCM connector to the 3-4 shift solenoid is the PCM's control wire —it delivers the ON signal when the PCM wants to engage overdrive.
In this test, we'll check that this wire isn't shorted to Ground. A short to Ground here would cause the solenoid to engage when it shouldn't, or prevent proper control from the PCM.
We'll test it both with the transmission connector disconnected and again with it connected to ensure no hidden shorts exist in the harness or at the connector.
OK, let's get this pot of water boiling:
- 1
Set your multimeter to Ohms mode.
- 2
Keep the battery disconnected from its battery negative (-) cable.
- 3
Keep the PCM disconnected from its 3 connectors.
- 4
Disconnect the transmission connector at the transmission case.
- 5
Probe pin 21 of the WHITE PCM connector with one multimeter lead.
NOTE: Use a thin, non-damaging probe to avoid spreading the terminal. - 6
Touch the other multimeter test lead to the battery negative (-) cable terminal.
You can also Ground the test lead on a clean and rust/paint free bolt or bracket on the engine or frame. - 7
You should see infinite resistance (open circuit) or "OL" on a digital meter —indicating the wire is NOT shorted to Ground.
- 8
Reconnect the transmission connector and repeat the test.
- 9
You should see infinite resistance (open circuit) or "OL" on a digital meter —indicating the wire is NOT shorted to Ground inside the transmission.
- 10
Have a helper gently wiggle the transmission connector and the wiring coming out of it while you watch the multimeter.
Be sure to also wiggle any visible sections of the wiring harness leading from the connector into the engine bay.
You're looking for any sudden drop in resistance or a momentary short to Ground. This step is critical —intermittent faults often only show up under movement or vibration.
Let's interpret your test result:
CASE 1: No continuity to Ground with the transmission connector disconnected or connected. This is the correct result and tells us the overdrive solenoid control wire is not shorted to Ground.
Your next step is to go to: TEST 4: Checking For Shorts Between Solenoid Control Circuits.
CASE 2: Continuity to Ground exists with the transmission connector disconnected. This indicates the BRN wire is shorted to Ground somewhere between the PCM and the transmission.
You'll need to inspect the wiring harness for sections where the insulation has melted or been rubbed through —often caused by the harness chafing against a sharp edge on the transmission or engine.
CASE 3: No continuity to Ground with the connector disconnected, but continuity appears when connected. This suggests the short to Ground exists inside the transmission —possibly in the internal harness or at the solenoid itself.
If everything on the outside of the transmission looks good —no signs of melted wires, chafing, or physical damage to the harness— then it's time to consider dropping the transmission pan to inspect the internal wiring.
But keep in mind: this is a big step, so make absolutely sure you've ruled out all external harness issues first.
TEST 4: Checking For Shorts Between Solenoid Control Circuits
Each shift solenoid and pressure control solenoid in your transmission is controlled by its own independent PCM circuit.
If any of these wires are shorted together —either in the harness or inside the transmission— it can confuse the PCM and trigger trouble codes like P0753.
In this test, we're going to verify that the 3-4 shift solenoid control circuit (pin 21) is completely isolated from the TCC solenoid (pin 11) and the governor pressure solenoid (pin 8).
Shorts between these circuits are rare, but they can happen —and when they do, they're often overlooked.
- 1
Set your multimeter to Ohms mode.
- 2
Keep the battery disconnected from its battery negative (-) cable.
- 3
Keep the PCM disconnected from its 3 connectors.
- 4
Disconnect the transmission connector at the transmission. This isolates the circuits during the first phase of testing.
- 5
Probe pin 21 and pin 11 of the WHITE PCM connector. You're checking for a short between the 3-4 shift solenoid and TCC solenoid circuits.
- 6
Now probe pin 21 and pin 8 of the WHITE PCM connector. This checks for a short between the 3-4 shift solenoid and governor pressure solenoid circuits.
- 7
Reconnect the transmission connector and repeat both tests. This helps confirm if a short exists inside the transmission or its connector.
- 8
Watch for any continuity between the pins. You should see infinite resistance or "OL" between circuits —no connection should exist.
- 9
Have a helper gently wiggle the transmission connector and the wiring coming out of it while you watch the multimeter.
Be sure to also wiggle any visible sections of the wiring harness leading from the connector into the engine bay.
You're looking for any sudden drop to 0 Ohms. This step is critical —intermittent faults often only show up under movement or vibration.
Let's interpret your test result:
CASE 1: No continuity between any of the pins (21↔11 and 21↔8), with or without the transmission connector connected. Perfect —these circuits are electrically isolated as they should be.
At this point in time, whatever is causing DTC P0753 isn't present. There's a good chance that the PCM has an internal fault.
Don't replace the PCM just yet, take a look at this important section: What If The PCM Is Bad?
CASE 2: Continuity exists between pin 21 and 11, or pin 21 and 8, even with the transmission connector disconnected. This indicates a short between the solenoid control wires somewhere in the harness.
To resolve DTC P0753, your next step is to carefully inspect the wiring harness for damaged insulation or exposed wire along the path back to the PCM. Look for signs of rubbing, melting, or pinching.
Once you locate and repair the damaged section causing the short between wires, the transmission issue should be resolved.
CASE 3: No continuity with the transmission connector disconnected, but continuity appears when it's connected. This points to a short within the internal transmission circuits (faulty internal wiring harness).
If everything outside the transmission checks out —no melted wires, chafing, or visible damage to the external wiring harness— then it's time to consider dropping the transmission pan to inspect the internal wiring and solenoid connections.
Just remember: dropping the pan is a bigger step, so make absolutely sure all external harness issues have been ruled out first.
Common Problems With The 8-Wire Transmission Connector
The 8-wire connector at the transmission case is a known failure point on Dodge Ram trucks. Over time, it's common for the metal terminals inside the connector to break away from their wires, especially due to heat, vibration, or age.
Another frequent issue is the round female terminals losing tension, meaning they no longer make solid contact with the matching male terminals inside the transmission. This leads to intermittent or total circuit failure.
If you're replacing this connector, there's one rule that cannot be stressed enough:
- Do not use butt connectors to splice the wires.
If you use butt connectors, you are guaranteeing yourself problems down the road. As the vehicle vibrates and the wiring moves, butt connectors lose their grip —leading to intermittent faults, poor continuity, or no contact at all.
The correct way to install a new connector is to solder the wire splices and seal them with heat-shrink tubing.
Once the repair is complete, make sure the wiring is properly secured and supported, so it doesn't hang or move freely. Dangling wires put stress on the connector and its terminals and will eventually lead to another failure.
What If The PCM Is Bad?
A faulty Powertrain Control Module (PCM) can cause a persistent P0753 trouble code and no overdrive —but it's very rare. Before you even think about blaming the PCM, you need to rule out all the usual suspects first.
There's a long list of more common issues that can trigger this code or prevent the 3-4 shift solenoid from working properly. Before pointing fingers at the PCM, make sure these are all checked and cleared:
- The 3-4 shift solenoid itself (bench test and resistance check).
- Damaged wiring (rubbed-through insulation or melted areas) between the solenoid and PCM.
- No power getting to the solenoid (verify ignition-switched 12V at the connector).
- Open circuit on the BRN wire back to the PCM.
- BRN wire shorted to Ground somewhere between the solenoid and PCM.
- Internal short or cross-contact inside the engine wiring harness.
- Incorrect transmission fluid level or poor fluid condition.
- Internal mechanical damage inside the transmission.
Also, drop the transmission pan and inspect the fluid. If you find a ton of clutch dust, metallic sediment, or chunks of friction material, that's a red flag.
Internal wear or damage to the clutch packs (especially overdrive clutches) can easily cause shift issues and confuse the PCM into setting a code like P0753.
If everything else checks out, and you're still leaning toward a PCM issue, get a second opinion from an experienced technician. PCM failures are uncommon —and expensive— and jumping the gun can lead to wasted time and money.
One More Thing To Watch For: If you plan on installing a used PCM, and it isn't properly flashed with your vehicle's VIN, it can cause all kinds of driveability and communication problems.
The PCMs may look identical and plug right in, but the programming inside is vehicle-specific. Always make sure a used or replacement PCM is correctly flashed to match your truck's exact specs before installation.
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:
Here's a sample of the tutorials you'll find in the index:
- How To Test The Fuel Pump (1992-2003 5.2L, 5.9L V8 Dodge Ram Pickup).
- How To Test The MAP Sensor -P0107, P0108 (1997-2003 5.2L, 5.9L V8 Dodge Ram Pickup).
- How To Test Engine Compression (1989-2003 5.2L, 5.9L V8 Dodge Ram Pickup).
- Troubleshooting A Blown Head Gasket (1989-2003 5.2L, 5.9L V8 Dodge Ram Pickup).
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