1996 Mazda 626 OBD Codes P1506 and P0141

JIGGIN23

MEMBER
1996 MAZDA 626
4 CYL
2WD
AUTOMATIC
125,000 MILES

I have a 1996 Mazda 626 that I need to get the emissions done on. The check engine light had been on for quite some time. I took it in to get the codes fixed, and there were two codes, p1506 and p0421. For the p0421 they replaced a leaking front exhaust pipe and both o2 sensors, but said that it could be a bad converter. For the p1506 they replaced the idle air control motor. These repairs were very expensive, apprx. $2000 dollars, but I didn't know what else to do. A day after picking up my car, the check engine light came back on and I went to the auto parts store and had the codes pulled, the p1506 is back (making me think the IAC motor probably did not need to be replaced in the first place) and now there is a p0141. I called the place and they said the converter probably needs replaced which is about another $700. Is there anything I can have them check, or should I just have them replace the converter? Thanks for all your help

Update: Went and bought an actron reader. Intermittently p0136 will register as well. The P0141 always shows up and the p1506 doesn't always show up.

3 Replies

KHLOW2008

MECHANIC
41,814 POSTS

Hi jiggin23,

Thank you for the donation.

P0141 = Downstream HO2S Heater CKT Malfunction.

This is not an O2 problem but the heated circuit and it should not be related to the catalytic converter. Either the HO2S sensor or its wiring circuit is faulty.

P0136 = Downstream HO2S CKT Malfunction.
This is either due to a fault in the HO2S or the catalytic converter.

P0421 = Catalyst efficiency.
This is most probably due to a bad catalytic converter but a faulty O2 sensor can cause it, vice versa it can cause a bad O2 reading and indicator malfunction.

I have attached a diagnostic for the P1506 and it is self explanatory.

Emission trouble shooting sometimes can be sticky as engine performance can cause it to happen as well. When burning rich or lean, maybe due to vacumn leakages, air flow clogging, fuel pressure low etc can cause it to happen so it would be best to do test and checks first before proceeding with replacement of parts.

I believe the catalytic converter is due for replacement.

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Monday, December 8th, 2008 AT 3:21 AM

JIGGIN23

MEMBER
2 POSTS

So for an update, I replaced the catalytic converter myself, all went well. Still getting codes P0141, P0136 and intermittent P1506. Took it into the same shop, they say that the exhaust manifold needs to be replaced, does this sound like a good diagnosis? Is this something I could replace myself? Thanks for all your help.

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Monday, December 29th, 2008 AT 8:40 AM

KHLOW2008

MECHANIC
41,814 POSTS

Hi jiggin23,

To replace the exhaust manifold is not difficult and you should be able to do it yourself. However the bolts and nuts tends to stick so it is best done when the engine is hot and some rust removing spray onto the nuts before removing would be recommended.

Exhaust manifolds only needs to be replqaced if they are cracked and would emit noises when engine is running. To perform visual and leakage checking, remove the exhaust shield and look for cracks. Start engine and listen for leaking noise which would normally sould like hollow " put put " and would tend to change pitch when engine is revved slightly.

EXHAUST MANIFOLD
Removal & Installation
Disconnect necessary electrical connectors, hoses and cables.
Remove exhaust manifold shield.
Disconnect exhaust pipe from exhaust manifold.
Remove exhaust manifold bolts and nuts.
Remove exhaust manifold.

To install, reverse removal procedure.
Tighten exhaust manifold bolts to specification.