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.
Contents of this tutorial:
- Symptoms Of A Bad 2-4 Shift Solenoid (DTC P0755).
- What Tools Do I Need?
- Where To Buy The Chrysler Solenoid Pack.
- Circuit Descriptions Of The Chrysler Transmission Solenoid Pack.
- TEST 1: 2-4 Shift Solenoid Resistance Test.
- 2-4 Shift Solenoid Test Conclusion.
- Chrysler Transmission Solenoid Pack Tutorials.
You can find this tutorial in Spanish here: Cómo Probar Código P0755 (Solenoide De Cambio B) (at: autotecnico-online.com).
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:
- Multimeter
- Don't have one or need to upgrade your analog multimeter to a digital multimeter, check out my recommendation here: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link).
- 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 this scan tool: ZM301 OBD2 Scanner Diagnostic Tool (Amazon affiliate link).
Where To Buy The Chrysler Solenoid Pack
Your local auto parts store (like AutoZone or O'Reilly Auto Parts) will carry the Chrysler solenoid pack and will be more than happy to sell you one at a cost of US$150 to $200, which is quite expensive.
Another alternative you may want to explore, is buying it online and saving a few bucks. Below, you'll find two links (to the same place) so that you can shop and compare and see what option is best for you!
Disclosure: As an Amazon Associate, I earn from qualifying purchases. Buying through these links helps support this site at no extra cost to you. Thanks for your support —it really means a lot!
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 solenoid 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 | ||
|---|---|---|
| Pin | Wire Color | Description |
| 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.
TEST 1: 2-4 Shift Solenoid Resistance Test
OK, to get this show on the road, I'm gonna' ask you to check the resistance of the 2-4 Shift Solenoid.
You'll need to disconnect the solenoid pack's 8-wire connector and test the resistance of solenoid pack's pins #4 and #8.
Pin #4 is the one that feeds power (10 to 12 Volts) to the 2-4 Shift Solenoid and Pin #8 is the one that feeds the activation signal.
NOTE: It's best that you do this test with a cold engine or you run the risk of getting burned by a hot engine and/or transmission. Be careful, use common sense and think SAFETY.
OK, this is what you'll need to do:
- 1
Disconnect the solenoid pack's 8-wire electrical connector.
This is an on-car test, so you don't have to remove the solenoid pack to test it. If you already have it off -that's no big deal, you can still use the info in this test tutorial to check it. - 2
Place you trusty multimeter in Ohms mode.
- 3
With the red lead, probe the metal male terminal labeled with the number 4 in the photo above.
- 4
Probe the metal male terminal labeled with the number 8 with the black multimeter test lead.
- 5
Your multimeter should register between 0.5 to 9 Ohms if the solenoid is OK.
Let's take a look at what your test results mean:
CASE 1: The multimeter registered the indicated Ohms. This tells you that the 2-4 Shift Solenoid (within the solenoid pack) is OK.
Since a trouble code P0755 is lighting up the check engine light on your instrument cluster, the next steps are:
- Check the continuity of circuit #8 between the Transmission Control Module and the solenoid pack's connector.
- Check the physical condition of the solenoid pack's connector and the round metal terminals inside of it for damage.
The above steps are beyond the scope of this article, but at least now you know what direction your troubleshooting needs to take.
CASE 2: The multimeter DID NOT register the indicated Ohms. Double check that you're testing the correct metal male terminals on the solenoid pack and retest.
If you still don't see the indicated resistance in Ohms, then the 2-4 Shift Solenoid is bad. You'll need to replace the solenoid pack assembly to resolve the problem.
2-4 Shift Solenoid Test Conclusion
Over the years, working as diagnostic tech in an automotive repair shop, I've replaced quite a few bad Chrysler solenoid packs, so in this section, I want to share a couple of personal suggestions that I think will help you:
- Whenever any of the shift solenoids, inside the solenoid pack, go bad, the transmission will go into LIMP IN mode. This means the transaxle (this is the correct technical name for a front-wheel drive automatic transmission) will stay and run in 2nd gear only.
- A bad 2-4 Shift Solenoid will not cause your transmission to slip.
- If your vehicle's transaxle is slipping, then replacing the solenoid pack will not help since slippage is a direct result of internal transaxle damage (burned clutch discs, broken/worn internal hard parts, etc).
- Can a bad solenoid pack cause the transaxle to go bad?, the answer is YES if you don't take care of the problem as soon as possible and/or continue driving it for extended amounts of time/distance in LIMP IN mode.
Hope this tutorial helped!
Chrysler Transmission Solenoid Pack Tutorials
The following tutorials relate to this transmission solenoid pack tutorial:
- Testing Diagnostic Trouble Code P0750 (Low Reverse Shift Solenoid Malfunction).
- How To Test Diagnostic Trouble Code P0760 (Overdrive Solenoid Malfunction).
- How To Test Diagnostic Trouble Code P0765 (Shift Solenoid D Malfunction).
If this info saved the day, buy me a beer!
