P2548: Torque Management Request Input Signal B
What to do
The symptoms and the reasoning are the same as the A circuit: a flat engine, or harsher gearchanges, caused by a wire between modules rather than by anything in the engine itself. Worth mentioning that both an A and a B code stored together points at something shared — a connector or a common ground — rather than at two separate faults, which is usually the quickest thing to check.
What this code means
A fault in the second torque management request circuit. What a torque reduction request is, and why the engine module obeys it, is at P2544.
There are two lines for two reasons, and it is worth knowing which applies to a given vehicle because it changes what a fault on one of them means.
- More than one system requests reductions. On some designs the transmission has its own line and the stability control system another, so the two arrive separately and can be told apart.
- A single request is carried on two wires with a defined relationship, so that no single wire fault can either invent a request or suppress one. This is the same reasoning that puts two sensors in an accelerator pedal (P2138) and two request lines between the climate panel and the engine module (P2522): where a signal matters, one wire is a value and two are a check.
On a vehicle of the second kind, a fault on B alone usually means the pair no longer agree, and the module falls back to whichever behaviour is safe — which in the case of torque is to assume the reduction was requested.
Likely causes
Start here
- Damaged wiring harness · moderate
- Corroded or loose connector · easy
- Wiring shorted to ground · moderate
Less common
- Faulty transmission control module · specialist
- Faulty stability control module · specialist
Rare
- Faulty engine control module · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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