This tutorial will help you diagnose a P0755 (OBD II) or Code 42 (OBD I) Transmission diagnostic trouble code (DTC). You'll learn how to do a resistance test of the 2-4 Shift Solenoid that's inside and part of the Transmission's Solenoid Pack.
OK, to make it as easy as possible to navigate this article, here are its contents at a quick glance:
- Symptoms of a BAD 2-4 Shift Solenoid (DTC P0755).
- What Tools Do I Need?
- Circuit Descriptions of the Chrysler Transmission Solenoid Pack.
- TEST 1: 2-4 Shift Solenoid Resistance Test.
Symptoms of a BAD 2-4 Shift Solenoid (DTC P0755)
When the 2-4 Shift Solenoid (also known as Shift Solenoid B), inside the Transmission Solenoid Pack, goes bad, you're gonna' see two specific symptoms, these are:
- The check engine light (CEL) will be lit nice and bright on your Chrysler vehicle's instrument cluster.
- If OBD II equipped, the trouble code you're gonna' see stored in the PCM's memory is a P0755: 2/4 Solenoid Circuit Malfunction.
- If you're using a very simple code reader, the code will be described as: P0755: Shift Solenoid B Malfunction (OBD II equipped only).
- If OBD I equipped, you'll see trouble code 42: 2-4 Solenoid Circuit.
- The Transmission will not shift gears:
- More specifically, it'll stay in 2nd gear no matter what speed you're driving the vehicle.
- This is called in tech terms: Limp In mode.
It stinks that you're having this issue (P0755 or code 42), but the cool thing is that it's not that hard to test this yourself and replace the Solenoid Pack if indeed the 2-4 Shift Solenoid is BAD.
What Tools do I Need?
The most important tool that you're gonna' need is a multimeter. Your multimeter can either be a digital multimeter or an analog multimeter.
A Scan Tool is becoming a must have tool, but isn't necessary to use the info in this test tutorial of the 2-4 Shift Solenoid.
Here are some of my suggestions:
- Don't have one or need to upgrade your analog multimeter to a digital multimeter, check out my recommendation here: Abe's Multimeter Recommendation.
- Scan Tool
- As I mentioned above, you don't need to use a scan tool to take advantage of the test info in this tutorial, but it does come in handy to read any trouble codes.
- If you don't own a Scan Tool yet, I recommend taking a look at these 2 articles I've written: Scan Tool Essentials You Should Know! (at: troubleshootmyvehicle.com) and Actron CP9580 Scan Tool Review (also at: troubleshootmyvehicle.com).
Circuit Descriptions of the
Chrysler Transmission Solenoid Pack
Now, just in case you're not aware... the 2-4 Shift Solenoid (Shift Solenoid B) is part of the Transmission Coil Pack (this also means that if your tests indicate it's BAD, you'll need to buy the whole Solenoid Pack to solve the problem).
The Transmission Coil Pack is bolted to the Transmission (see the photo at the top of this page). A connector with 8 wires connects to the Solenoid Pack.
2 of those 8 wires are the ones that feed Power and the activation signal to the 2-4 Shift Solenoid and in this section, I'll identify them for you. This is info you'll need to know to test the Solenoid.
|Chrysler Solenoid Pack Connector Pin outs|
|1||Yellow w/ Black stripe *||2-4 Pressure Switch|
|2||Dark Green *||Low/Reverse Pressure Switch|
|3||Orange w/ Black stripe *||Overdrive Pressure Switch|
|4||Red *||Power (10 to 12 Volts DC)|
|5||Pink *||Underdrive (UD) Solenoid|
|6||Brown *||Overdrive (OD) Solenoid|
|7||Light Blue *||Low/Reverse Solenoid|
|8||White *||2-4 Shift Solenoid|
* Your specific Chrysler, Dodge, Plymouth vehicle may have different colors.
One last thing before we move on to the next page (and start testing)... the Solenoid Pack will have the above 8 numbers embossed on it. This will further aid you in identifying the metal male terminals you'll need to test in the next page.