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rdeep 09-29-2012 07:16 PM

YJ won't run with MAP connected
Worked all day changing all the MAP, TPU, O2, and Intake temp sensors, plugs, rotor, cap, changed the capacitors in the ECU and still have the same symptoms. 4 cyl, 5 speed. Will not crank with the MAP sensor plugged up. With the MAP unplugged, it will crank and run rough until the check engine light comes on. Then it runs OK up to around 4200 RPM. At 4200 it cuts out much like a rev limiter. The error codes are 12, 14 twice, 33, and 15. The check engine light comes on as soon as you turn the key on for a few seconds then goes out whether the MAP is plugged in or not. Checked the power to the MAP and it is OK(4.8V) when unplugged and about 40 mV when plugged in. Have tried 4 different MAP sensors with the same results. Anybody have any suggestions?? Thanks.

2xs 09-29-2012 08:20 PM


cakes567 09-29-2012 10:26 PM

Re set the computer by un hooking the battery for a few seconds then hook it back up. Also just to see what would happen.... fire it up with the map unplugged and while its running plug it in see what it does

rdeep 09-30-2012 07:43 AM

Have reset the computer several times with the same results. Cranked without the MAP and then plugged it in. Will run above about 3000 RPM which makes sense as the voltage would drop at higher RPM. Engine sputters below 3000 and stalls below 1800. When idling and plug in the MAP, engine dies as if the key was turned off. Checked the feed voltage into the MAP while connected and it's way out of spec. Supposed to be 5V +- .5 but is 350 mV. What confuses me is that when it is unplugged the connector reads 4.85 V. I would think that the MAP was bad, but as posted before, have tried with 4 different MAP sensors. Thought it might be a ground problem so I checked between the + on the connector and the - on the battery and it was fine (MAP disconnected). I'm guessing now it is the MAP circuit in the ECU. Thanks for the help.

2xs 09-30-2012 02:56 PM


"The MAP sensor mounts against the firewall and reads manifold pressure. At connector terminal ‘B,’ with the ignition switch ON and engine not running, voltage should read 4-5 volts. This reading should drop 1.5-2.1 volts on a hot engine idling without a load in neutral or Park. Supply voltage from the ECU harness, read at terminal ‘C’ of the MAP sensor, should be 5 volts plus-or-minus 0.5-volts with the ignition ON. If out of range on voltareadings, replace the MAP sensor."
Source: Moses Ludel's 4WD Mechanix Magazine - Tuning and Troubleshooting the 2.5L Jeep TBI Four (I dont have a manual handy)

Im curious, what is your CTS reading, and when you plug in your MAP sensor, watch the fuel spray, does it stop or spray more?

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