P0846 Chrysler: 2/4 Pressure Switch Rationality - Diagnosis, Causes, and the Real Fix

P0846 shows up on Chrysler, Dodge, Jeep and Ram vehicles as 2/4 Pressure Switch Rationality (the RFE service information calls the same switch the 2C switch). It is a rationality code, not a circuit code, which means the computer is not complaining that a wire is cut - it is complaining that the switch is reporting the wrong thing at the wrong time. Most drivers notice it as harsh shifting, slipping, or the transmission dropping into limp mode and refusing to leave second gear.

It turns up most often on the 62TE six-speed and across the 45RFE family. Knowing what the switch actually does is the difference between a part swap that fixes it and a teardown that did not need to happen.

What the 2/4 pressure switch is watching

These transmissions have no bands, so every gear is made by applying and releasing clutches, and the computer needs proof each clutch did what it was told. Per the Chrysler 45RFE/545RFE service procedure for P0846, the transmission system uses five pressure switches to monitor fluid pressure in the LR, 2C, 4C, UD and OD clutch circuits, and those switches are continuously monitored for the correct states in each gear. The DTC sets when the 2C switch reads open or closed at the wrong time in a given gear, monitored continuously with the ignition on, engine running, and the transmission in gear.

Here is the expected switch state table from that same Chrysler procedure. It is the most useful diagnostic tool you have, because it tells you whether your live data is lying:

*Chrysler notes the L/R switch may be open when rolling in Neutral or at low oil temperatures, and that L/R is closed if output speed is below 100 rpm in Drive and Manual 2. Source: 2007 Grand Cherokee 45RFE/545RFE P0846 service procedure.

Diagnosis: work the code in this order

1. Check for other TCM power-input codes first. The factory procedure starts here. If the module has a power or ground problem, every switch reading is suspect and chasing P0846 is wasted work.

2. Look at how many pressure-switch rationality codes are stored. This is the branch point. If all the pressure switches read CLOSED in the DTC event data, Chrysler sends you to P0882 diagnostics instead - that is a power-supply pattern, not a switch pattern. If all the switches read OPEN, you are looking at a pressure problem, not an electrical one.

3. Compare line pressure to desired line pressure. The factory threshold is specific: if line pressure is less than 40 psi and significantly below desired line pressure, stop and fix the pressure problem. Chrysler's order is fluid level first, then the primary oil filter seal - checked for a split, a crack, or improper installation - and then the main regulator valve in the oil pump. A split filter seal is a cheap, common cause of a whole board of pressure switch codes.

4. Check the sense circuit. If the switch data looks wrong but pressure is fine, the T147 2C pressure switch sense circuit gets tested for an open, a short to ground, and a short to another circuit, with 5.0 ohms as the pass/fail line in each test. Chrysler warns not to probe the PCM harness connectors directly, since that damages the terminals, and specifies the Miller #8815 breakout tool instead.

5. The safety step people skip. Before running the scan tool's pressure switch test, the factory procedure requires removing the starter relay from the PDC. Skip it and the vehicle can be started in gear. Chrysler also warns that leaving the relay in can cause a transmission no-response condition.

6. Check balls and clutch circuit leakage. If the code set outside Park, Reverse and Neutral and the electrical side checks out, Chrysler has you inspect the No. 5 and No. 7 check balls for cuts or damage, and look for an extra check ball downstream of the No. 7 socket. Then air-check the 2C clutch circuit for excessive leakage; the circuit contains a small bleed orifice, so a little leakage is normal. Excessive clutch debris in the pan at this point means the 2C clutch itself is the real repair.

The fix: the solenoid pack is the usual answer

Run every branch of that procedure and the endpoint, over and over, is the same: replace the transmission solenoid/TRS assembly. The pressure switches are not separate serviceable parts - they live inside the solenoid pack. On the 62TE, Sonnax documents that the solenoid pack contains six shift solenoids, one line pressure solenoid, a temperature sensor and five pressure switches, while the line pressure sensor and the TCC variable-force solenoid bolt directly to the valve body and are not part of the pack. That is why a bad 2/4 switch is a pack replacement, not a switch replacement.

Writing for Transmission Digest, Sonnax TASC Force member Jeff Parlee lists the 62TE's six shift solenoids as low/reverse (normally closed), 2/4 (normally open), low clutch (normally closed), underdrive (normally open), overdrive (normally closed) and direct clutch (normally closed). All six look identical. His shop test is to blow compressed air into the open end: if the air is blocked it is normally closed, and if air comes out of the holes between the two large O-rings it is normally open. Sonnax adds that solenoid resistance testing should be done at approximately 70 degrees F, since resistance moves with temperature.

Sonnax also flags a fix that is not the pack itself. Its Solenoid Spacer & Service Kit 44836-02K, which fits all 62TE and 65/66RFE units plus 2018-and-earlier 68RFE and 2004-and-later 45RFE/545RFE, is listed specifically as helping cure codes 841, 846, 871, 876 and 988. If your codes come and go and the switch data looks correct most of the time, that intermittent pattern is worth chasing before condemning the pack outright.

One more family failure worth ruling out: Sonnax identifies solenoid switch valve bore wear as the most common wear area in the shared 41TE and 45RFE valve bodies, producing bind-up, failsafe mode, no lockup and codes 841, 868, 871, 988, 1775 and 1776. The original valve used a 0.420" large spool; a revised design went to 0.453" around the 2006 model year on the 41TE branch and around 2010 on the 45RFE branch, with both sharing 0.453" outer plugs. Sonnax stresses measuring the valve before ordering tooling, and vacuum testing to decide whether the bore needs work at all. We cover that failure in detail in our 45RFE and 545RFE P0871 limp mode guide.

Replace while you are in there

The pan is off and the fluid is out, so do not make this job twice:

• Filter and pan gasket. A split or improperly installed primary filter seal is one of Chrysler's own listed causes of the low line pressure that sets this code. Fit a 62TE transmission filter with pan gasket rather than reusing either.
• Solenoid pack spacer and seals. Per the Sonnax service kit listing above, this is a documented contributor to the 841/846/871/876/988 code cluster.
• Inspect the No. 5 and No. 7 check balls while the valve body is accessible - they are on Chrysler's own cause list for P0846.
• Route the wiring correctly on reassembly. Parlee's warning is blunt: use all the clips and routing troughs in the plastic body of the solenoid pack, because failing to do so may result in wiring damage - and damaged wiring is exactly what sets this code again.

Ram and Jeep owners working the heavy-duty side of the same family can start with a 68RFE shift solenoid block pack, and the full range is in our transmission solenoids collection.

Cost and effort

This is a pan-down job, not a teardown. The solenoid/TRS assembly is internal and mounted on the valve body, so the work is drain, drop the pan, pull the filter, unbolt, swap and reseal. A DIYer with a lift or good jack stands should plan on a half day plus fluid; a shop bills it as valve-body access rather than an overhaul.

The last step is what trips people up. Chrysler's procedure specifies the Quick Learn procedure with a scan tool after module replacement, plus the transmission verification test after any repair on this unit. Without a tool that can run Quick Learn, a correct part swap can still drive badly, because the adaptive shift values are stale. Budget for that tool or that shop visit before you start.

FAQ

Can I drive with P0846? You can move the vehicle, but the transmission will typically be in limp mode - locked in a single gear with no converter lockup. That loads the clutches and converter far harder than normal, and if the cause is low line pressure, you are burning clutches every mile. Diagnose it before you rack up distance.

Is P0846 always the solenoid pack? No, and that is why the order matters. Chrysler's own cause list includes an open or shorted 2C sense circuit, excessive fluid leakage in the 2C clutch circuit, a cut or damaged No. 5 or No. 7 check ball, an extra check ball downstream of the No. 7 socket, low line pressure, the powertrain control module, and wiring and connectors - before it names the solenoid/TRS assembly. The pack is the most common answer, not the automatic one.

Why do I have P0846 plus P0871 and other switch codes at once? Multiple simultaneous rationality codes point away from one bad switch. Chrysler routes you to check whether all switches read closed (a power-supply pattern that redirects to P0882) or all read open (a pressure pattern). Sonnax's service kit listing also ties the 841/846/871/876/988 cluster to the solenoid spacer. Our 62TE harsh shift and limp mode guide walks that pattern through on the 62TE specifically.

Sources

• Chrysler / Jeep Service Information - P0846-2C Pressure Switch Rationality, 2007 Grand Cherokee (45RFE/545RFE) diagnostic procedure
• Sonnax - 62TE Solenoid Identification & Connector Pin Out
• Sonnax - All in the Family: Identification & Repair of Chrysler Solenoid Switch Valve Problems
• Sonnax - Chrysler 62TE parts and symptom index (Solenoid Spacer & Service Kit 44836-02K)
• Transmission Digest - Solenoid-Pack Information for the Chrysler 62TE, Jeff Parlee (Sonnax TASC Force)