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OBD-II Code

P0978

Severity

Not yet reviewed

Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.

Can you drive it

We cannot say

Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.

Indicative cost (USD)

$300–$1,500

From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.

P0978 is the Shift Solenoid B Control Circuit Intermittent — the TCM sees SS-B circuit voltage drop out of normal operating range, then return, without staying in a stable short or open.

How a shop works this

Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.

  1. Note every code that is set, not just this one.

    Codes that appear together usually narrow the cause faster than any one of them read alone.

  2. Read the freeze frame — the conditions the fault was recorded under.

    Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.

  3. Confirm the fault is current rather than history.

    Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.

  4. Then follow the diagnostic notes further down this page, in the order they are written.

    They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.

If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.

Common symptoms

  • Check engine light
Read the full diagnostic procedureP0978 is the Shift Solenoid B Control Circuit Intermittent — the TCM sees SS-B circuit voltage drop out of normal operating range, then return, witho…

P0978 is the Shift Solenoid B Control Circuit Intermittent — the TCM sees SS-B circuit voltage drop out of normal operating range, then return, without staying in a stable short or open. Intermittents on shift solenoids cause non-reproducible harsh shifts, brief flares, or single-event limp-mode trips that clear before the customer can show you.

Cheapest-first

  1. freeze-frame data is your best friend here — pull the snapshot, note the fluid temp, vehicle speed, and gear range when the code set, and replicate those conditions on a road test with a scan tool live-recording SS-B commanded state and circuit voltage.
  2. Then wiggle-test the case connector and the harness route between TCM and trans with the engine running and a scan tool live on SS-B; movement that toggles the PID points at the connector or chafe point.
  3. Ohm SS-B pin-to-pin at the case both cold and at full operating temp — a winding that ohms 14 ohms cold and 4 ohms hot is breaking down thermally even though it passes a static check (spec should stay within 8-30 ohms across temp range; 19-31 ohms GM 4L60E, 9-16 ohms Ford 4R75W, 11-15 ohms Chrysler 545RFE pack, 10-15 ohms Toyota A340/A750).
  4. Ohms-to-ground should be >100k ohms on each pin both cold and hot — a reading that drops under load means partial short.
  5. Active current should track 0.5-1.5 A at full command; current excursions or dropouts during a road-test recording confirm the intermittent.
  6. Expensive-misdiagnosis caveat: on Chrysler 545RFE/68RFE intermittent P0978 is the textbook early-warning sign of pack thermal degradation — pack passes cold, faults hot, customer comes back.
  7. Single-circuit repair is not a supported procedure on this trans; full solenoid-pack replacement is the right answer once case connector and external harness are confirmed clean, and chasing connector cleanings or single-wire splices on a 545RFE/68RFE pack-failure case loses the customer's trust along with the come-back labor.
Vehicle-specific patterns1996-2007 GM 4L60E sets intermittent P0978 from a marginal case connector that loses pin-fit during temperature cycling — connector body replacement…
  • 1996-2007GM 4L60E sets intermittent P0978 from a marginal case connector that loses pin-fit during temperature cycling — connector body replacement is the documented fix, not contact cleaner.
  • 2003-2010Dodge Ram 1500/2500 with the 545RFE and 2007-up 68RFE sees P0978 as the documented precursor to outright pack failure, and aggregated AAMCO/RepairPal cost data places solenoid-pack replacement at $500-900 parts plus labor at independents in the 70k-150k mile window.
  • 2007-2013Ram HD with the Aisin AS69RC throws intermittent P0978 from valve-body sleeve wear scoring the SS-B plunger after a torque-converter shudder event — valve-body R&R, $800-1,400.
  • 2001-2010GM HD with the Allison 1000 (LCT1000) sets intermittent P0978 from PCS-2/PCS-3 wire chafe at the case-flange ridge under thermal expansion — Allison Transmission service guidance addresses this with a harness re-route procedure before solenoid or pack replacement.

Estimated repair$300 to $1,500.

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