P0726: Engine Speed Input Circuit Range/Performance

What does P0726 mean?

The transmission module needs engine speed for converter slip, shift quality and to check the turbine speed. Today it almost always arrives over CAN from the engine module with a validity flag; only GM's 2007 Allison 1000 tables show a separate engine speed sensor read by the transmission module. P0726 means the engine speed value is present but implausible. The Allison 1000, which reads its own sensor, flags a jump of 600 rpm within 0.15 s or noise of ±650 rpm, with the engine above 600 rpm and a gear engaged, after two trips. Saab's 9-3 of 2000, which receives the value over the bus, flags more than 7200 rpm for at least 10 s. The converter clutch is then locked out and shifts may be harsh. No signal at all is P0727.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Transmission warning lamp, possibly check engine light
• Torque converter clutch locked out
• Harsh shifts or limp mode
• Often an engine code (crankshaft sensor) as well

Common causes

• High Engine speed sensor at the transmission (Allison) dirty or faulty, loose contact
• Medium Interference (shielding, ground)
• Medium Wrong bus value from the engine module (crankshaft sensor problem)
• Low Transmission module

Likelihood is a general estimate across vehicles; your make and model may differ.