05 codes/transmission issue [Archive] - Chevy Malibu Forum: Chevrolet Malibu Forums

: 05 codes/transmission issue

06-21-2010, 04:18 PM
I'm working on an 05 Malibu with the 2.2 Ecotec that has begun to throw several codes at once and appears to not want to shift into the next gear when attempting to accelerate rapidly. Codes generated are:

P0130 O2 Sensor Circuit
P0134 02 Sensor Circuit No Activity Detected
P0300 Random/Multiple Cylinder Misfire Detected (Pending)
P0420 Catalyst System Efficiency Below Threshold
P0442 Evaporative Emission Control System Leak Detected

The transmission appears to function just fine unless you need to really give the car gas to pass a vehicle, then it will not shift into the next gear. This has happened at both 45MPH and 65MPH, and does not appear to be slipping, but rather simply not firing the solenoid to shift to the next gear. RPM is about 5500 in this instance. If you let off of the gas, it'll shift.

We replaced the transmission fluid and filter this past weekend as both scheduled maintenance and to see if the clutches were burning. The fluid was clean with no burn smell. After a test drive with the same shift issues and a fresh P0300 in pending status, we opted to replace the ignition control module. Things looked good that day, but P0420 is back again today.

The car has 140K on it, runs fine without any misses and does not appear to be impacted by the codes outside of the shifting issue described above. It sure doesn't appear to be a vacuum leak to me, since it runs well at low RPMs. The 02 and temperature sensors seem to be reading correctly, but they are original to the car. I have an OBDII scanner for my laptop and I'm able to get correct readings from all sensors that I can monitor. This motor does not have an EGR or PCV valve.

I'm confident that the codes are related to the shift issue, but I'm running out of ideas fast. Has anyone ever heard of anything like this? Could o2 sensors cause shift issues?

06-21-2010, 04:34 PM
The O2 sensor and/or catalytic converter is causing abnormal air/fuel ratios and thus manifold vacuum. I think the latter is what's causing the shifting anomaly. Do you have black smoke coming out the exhaust?

EDIT: Yours is 2005 and thus the shift points are probably based on the TPS but it's the same thing, i.e., the throttle body too wide open for the given vehicle speed.

06-21-2010, 08:07 PM
I've pulled the freeze frame data from the MIL generated today:

03 Fuel system status: open loop
04 Calculated load value: 28.6%
05 Engine coolant temperature: 198F
06 Short term fuel trim - bank 1: 0.0%
07 Long term fuel trim - bank 1:-7.8%
0B Intake manifold absolute pressure: 15.1psi
0C Engine RPM: 815RPM
0D Vehicle Speed: 0mph
0E Ignition timing advance for #1 cylinder: 7 degrees
0F Intake air temperature: 84.2F
10 Air flow rate: 86.11lb/min
11 Absolute throttle position: 29.0%

I'll check the tailpipe tomorrow and double-check the o2 sensor data. This is my little brother's car, so I won't be able to check until the afternoon.


06-21-2010, 10:23 PM
Since the car hasn't entered the closed loop yet, the only thing of use to me is the long term fuel trim of -7.8% which says it's been running somewhat rich (ECM had to compensate). Given P0130/P0134, O2 sensor 1 (the one closest to the exhaust manifold) is lazy and thus the fuel trim may just reflect that.

P0300 may be just the sign of lousy state of air/fuel management unless the spark plugs are fouled.

P0420 says O2 sensor 2 (the one after the catalytic converter) reads too close to O2 sensor 1. Again, since O2 sensor 1 is not trustworthy, the catalytic converter may not be shot yet.

P0442 could be a lot of things including leaky gas cap.

It would be so easy for me suggest replacing O2 sensor 1 (that's what I'd do). However, after that, P0420 may be partially plugged up catalytic converter as well. It's your call on how to proceed.

06-28-2010, 10:23 AM
I replaced the upstream o2 this weekend. By the time that we had gotten around to swapping it out, the car had logged both PO442 and PO440. I cleared those codes on Saturday, and so far no additional codes have been generated, however the transmission still seems to shift "late" when under stress. The o2 sensor was obviously bad - I've never seen one that had been physically damaged before. No P0300 codes have appeared since the ICM was replaced last week, however I was told this morning that the check engine light flashed a few times when the transmission shifted late while getting onto a highway.

Does the transmission need time to "learn" that it's healthy again. If not where do I go next?

Also - I can't believe that the o2 sensor just failed like it did. Surely something caused the damage.


06-28-2010, 11:23 AM
The EVAP system is checked at startup and thus the code(s) will probably come back in a couple of cycles.

There's no learing involved unless the battery was disconnected. The CEL flashing may be due to misfiring. I'm afraid that the abnormal shift points are consistent with a restrictive exhaust. A bad O2 sensor will toast the catalytic converter in a hurry. Diagnostics involve hooking up a pressure gauge (the same O2 sensor points) and measuring the exhaust backpressures before and after the catalytic converter at given RPMs.