MAP Sensor Replacement

Difficulty 1/50.25–0.5 hrs$25–601991-1995, 1996, 1997-2001

Short answer

Manifold Absolute Pressure sensor on the firewall. Failure causes rough idle, poor MPG, P0107/P0108. Five-minute replacement.

Carbureted V8 with orange valve covers and wiring in an engine bay — Photo: Alex Marc Wagner on Unsplash

The MAP sensor measures intake manifold vacuum to inform the ECU about engine load. On 4.0L XJ it is mounted on the firewall (Renix and early HO) or on the throttle body itself (later HO). A small hose runs from the manifold to the sensor on firewall-mount versions; check that hose for cracks - a leaky MAP hose mimics MAP sensor failure. Symptoms: rough idle, surging, poor fuel economy, hesitation, codes P0106-P0109. Mopar 56029405 fits 1991-2001. Two screws hold it; one electrical connector. Five-minute job. Beware that K&N over-oiled air filters can contaminate the MAP sensor diaphragm and cause identical symptoms - if you run K&N and see MAP codes, clean or replace the sensor and reapply less oil.

Why it works

Diagnosis is clear with a scan tool
Cheap fix

Trade-offs

K&N filter oil ruins MAP repeatedly

Tools required

Phillips screwdriver

Parts

Part	Vendor	Est. price
MAP sensor Mopar	Mopar/RockAuto	~$45

Sources

Cherokee Forum MAP

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