2003 1500 QC 5.7 Laramie

This is a code that I've been dealing with for a while. Comes on with normal mixed driving, this is the only code I have.

Steps taken:

• Verified fluid level
• Replaced Power Steering Pressure Switch
• Verified continuity for the switch signal wire from the switch connector through to pin 30 on the C3 connector of the PCM
• Verified continuity for the switch ground wire from the switch connector through to the G107 ground point and from the switch connector to the negative post of the battery (to verify I hadn't lost my body ground)

I don't see a data PID for that sensor to see what the PCM sees with my scan tool, but I have verified the circuit is healthy.

Tomorrow I'll be changing the fluid in the system and after that I'm not sure what else to try.

Anyone got any other ideas?

 

Not being able to see what the PCM is seeing is going to complicate matters...... Try testing continuity again, while moving the harness around. I have had wires that look just fine, and will test fine, but, won't carry the load when in actual use. (and man, those are fun to find....) Continuity test is an extremely low-load situation...... in actually operation, the wire may simply be inadequate.

 

Hello, thanks for the reply.

I've just tested the ground and signal wires and they're each able to carry a 4 amp load with no issues. Wiggling the harness didn't produce any drop outs.

I found this on the Autozone 2003 Dodge/Ram Truck RAM 1500 1/2 ton 4WD OBD II Trouble Code Lists Repair Guide

P0551 1T CCM 2001-03 Ram Power Steering Pressure Switch Circuit Failure Conditions:

• Vehicle driven at more than 56 mph for more than 30 seconds and the PCM detected a high voltage input on the PSPS circuit (pressure exceeds 500 psi). This is a normally open switch.

Possible Causes:

• PSPS sense circuit is shorted to ground PSPS is damaged or has failed PCM has failed

P0551 1T CCM 2004-05 Ram Power Steering Pressure Switch Circuit Failure Conditions:

• Engine running and vehicle driven at more than 40 mph for 30 seconds. If the PCM detected the PSPS signal remains open for 2 consecutive trips, this DTC will set. 3 good trips required to turn off MIL.

Possible Causes:

• PSPS sense circuit is open between the switch and the PCM PSPS ground circuit is open between the switch and ground PSPS is damaged or it has failed PCM has failed

No other codes, no other issues. PCM seems healthy.

Should the sense wire have a voltage potential on it? It's a pull down sensor so I'd assume I should be able to measure some voltage on the sense wire in an open circuit situation.

 

Ok some more data

Sensor wire shows 11.49 volts KOEO at the sensor connector
Ground wire shows 400mv between sensor connector ground wire and chassis ground KOEO

battery voltage is 12.35 KOEO

That's 11.49 volts with the plug connected AND disconnected. Tested the old sensor, it's failed closed. Circuit diagram shows it to be normally open. I'll test the new sensor later tonight when I have more time.

Could the high resistance on the ground wire be causing the circuit to not close? I wouldn't expect to see much over 100mv drop on that ground wire.

 

It's a possibility

 

Small update

I had some time tonight to mess with it some more. Disconnecting the pressure switch and jumping the leads (simulating the normally closed switch) results in the RPM's dropping by 150 or 200 or so. Removing the jumper causes the RPM's to rise again (simulating a high pressure switch opening). This is proper functionality.

Measuring the resistance of the new switch through the connector (back probed) I see ~130Ohms closed. The old switch measures 0.6Ohm closed.

Engine on, turning the wheels at idle and in park with 2krpm and turning the wheels, the new switch remained closed.

So either my rack is shot and can't make pressure (which I doubt since steering is normal and effortless), or I bought a new switch which is DOA.

Unsure of how to proceed. Obviously I can (and will) warranty the switch

 

Swap out the switch, see what happens. Wouldn't be the first time someone got a bad part, right out of the box......

 

Final update for anyone in the future searching for this trouble code...

My issue turned out to be the pins inside the connector for the pressure switch. The high resistance I measured did not remain when I tested the bare sensor. After inspecting the connector I discovered both female pins inside had opened, from [ ] box shape to more of a / \ shape

After massaging the pins back into shape and reassembling the connector, resistance is down close to 0 ohms, and the code has yet to return after 500+ miles of driving.

 

Good job! Congrats! Lots of helpful info here from you. Thanks for the update.