I went to Autozone and had my codes pulled, after the person working was trying to convince me it wouldn't work on a '94, especially a Volvo, and here's what I got (taken from the link in the sticky thread OBDII codes)...

P0137
O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)

P0141
O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)


My O2 sensor is disconnected from my exhaust, so that would explain one of them I assume. Any insight as to what those codes exactly mean would be a great help.

Thanks.

 

http://www.obd-codes.com/p0137

 

Thanks for the fast and detailed response. I located the other code on that site, and it refers to the O2 sensor. Would the two codes maybe have something to do with each other??

 

http://www.obd-codes.com/p0141
I think they are related to your disconnected O2 sensor but wait for experts to get on.

 

I think they are. I think one sensor is before the cat and the other one is after it, so if one is messed up it screws up the other one. Thank you for your replies though.

 

An unplugged rear O2 sensor will set both these DTCs (Diagnostic Trouble Code).

The four wire O2 sensors (such as these) have two circuits in them; two wires for each circuit.

One circuit is for the output signal; tells the ECM the O2 level in exhaust via an analog output signal.
Sensor unplugged => no signal to ECM; sets P0137.

Second circuit is for the sensor heater element within the sensor. The ECM actually provides current to this circuit to aid in heating up the sensor to operating temperature during engine warm-up period; sensor will not output proper signal until it is up to operating temperature. The ECM can determine if the heater element circuit is drawing proper current or not.
Sensor unplugged => no current draw to heater element from ECM; sets P0141.

So the question is, why is your rear O2 sensor unplugged?

BTW: '94 should be OBD1; shouldn't need to use scanner...
here's a link on how to pull OBD1 DTCs. It's also covered in the Hayne's manual.

 

That's cool, I didn't know that you could do that.

It's unplugged because the exhaust had a hole in it in the area of the rear o2 sensor. My Dad and I tried to fix it it by getting pipe from Auto Zone, however, they don't carry any pipe that's compatible with the size pipe on my car. So after we tried fixing it, there was no place to plug it in. I'm getting a new exhaust, so I will have a place to plug it back in soon and hopefully those codes will be cleared.

 

Now I have this P0137 code. The link to the code says that there can be 3 likely problems:
---------------------------------------------------------------------------------
Symptoms

There may be no visible symptoms to the driver, other than the MIL (Check Engine / Service Engine Soon) illumination.
Causes

A code P0137 may mean that one or more of the following has happened:

• Faulty o2 sensor Exhaust leak near the rear sensor
• Plugged catalyst
• Short to voltage on O2 signal circuit
• High resistance or open on O2 signal circuit

Possible Solutions

• Replace faulty sensor
• Repair exhaust leak near the rear sensor
• Check for restriction in catalyst and replace as necessary
• Repair short, open, or high resistance on o2 signal circuit

---------------------------------------------------------------------------------
1. A bad rear O2 sensor.
2. A bad catalyst.
3. An exhaust leak near the rear O2 sensor.

Where should I start? How would I know if my catalyst converter is bad?

 

Yes both codes means the sensor is unplugged. Both codes are for the same sensor.

 

I doubt that your cat would be bad. I've never really read a story of someone cat going bad, and I assume your talking about your yellow? I would check to sensors first, too bad they're so damn expensive that if they're not the problem that you just spent all that money on them.

Is there a way to test O2 sensors to see if they still work or not????

 

If a cat was bad it usually falls to pieces and cause rattles.
You can test the O2 sensor if you use an OBDII scanner and read real time.

 

Reading real-time method is definitely more simple than this:

Code 1-5-3 (Rear HO2S Signal)
1) If Codes 5-2-2 or 2-1-2 are stored, perform diagnosis for
these codes first. If fault is permanent or intermittent and signal is
too high, perform diagnosis as per Code2-1-2. If fault is permanent
and signal is too low, go to next step. If fault is permanent and
signal is faulty, go to step 8). If fault is intermittent and signal
is too low, go to step 9). If fault is intermittent and signal is
faulty, go to step 10).

2) Turn ignition off. Wait 2 minutes. Disconnect rear HO2S
Gray connector. Connect an ohmmeter between HO2S connector terminal
No. 4 and ground. If ohmmeter shows about 100 k/ohms, go to step 4).
If ohmmeter shows infinite resistance, go to next step. If ohmmeter
shows about zero ohms, check wiring between rear HO2S connector
terminal No. 4 and ECM terminal A34 for a short circuit to ground.

3) Turn ignition off. Disconnect HO2S connector. Ensure ECM
connector terminal contacts are clean and tight. Reconnect ECM.
Connect an ohmmeter between HO2S connector terminal No. 4 and ground. If ohmmeter reads about 100 k/ohms, source of code is poor contact at
ECM connector. If ohmmeter does not read about 100 k/ohms, check
wiring between rear HO2S connector terminal No. 4 and ECM terminal A34
for an open circuit.

4) Turn ignition off. Disconnect rear HO2S connector. Connect
an ohmmeter between HO2S connector terminal No. 3 and ground. If
ohmmeter reads about 200 ohms, go to step 7). If ohmmeter shows
infinite resistance, go to next step. If ohmmeter shows about zero
ohms, go to step 6).

5) Turn ignition off. Disconnect rear HO2S connector. Ensure
ECM connector terminals are clean and tight. Reconnect ECM. Connect an
ohmmeter between HO2S connector terminal No. 3 and ground. If ohmmeter reads about 200 ohms, source of code is poor contact in ECM connector.
If ohmmeter does not read about 200 ohms, check wiring between rear
HO2S connector terminal No. 3 and ECM terminal A19 for an open
circuit.

6) Turn ignition off. Disconnect rear HO2S connector.
Disconnect front HO2S Black connector. Connect an ohmmeter between
rear HO2S connector terminal No. 3 and ground. If ohmmeter reads about
200 ohms, test system using a new front HO2S. If ohmmeter does not
read about 200 ohms, check wiring between front HO2S connector
terminal No. 3 and ECM terminal A33, and wiring between rear HO2S
connector terminal No. 3 and ECM terminal A19 for a short to ground.

7) Turn ignition off. Ensure rear HO2S is connected. Start
and run engine at idle. Check voltage at rear HO2S. Voltage signal
should have left its bottom setting (-.165 volt) and stabilized
between .1-.9 volt within about 10 minutes. If reading is okay, source
of code is poor contact at rear HO2S connector. If reading is not
okay, retest using new rear HO2S.

8) If fault is permanent and signal is faulty, turn ignition
off. Wait about 2 minutes. Disconnect rear HO2S Gray connector.
Connect an ohmmeter between HO2S connector terminals No. 3 and 4. If
ohmmeter reads infinite resistance, check wiring between rear HO2S
connector terminal No. 4 and ECM connector terminal A34 for a short
circuit to rear HO2S connector terminal No. 3 and ECM connector
terminal A19. If ohmmeter does not read infinite resistance, test
using new HO2S.

9) If fault is intermittent and signal is too low, check
wiring between rear HO2S connector terminal No. 4 and ECM terminal
A34, and between rear HO2S connector terminal No. 3 and ECM terminal
A19 for an open circuit. Check ECM and rear HO2S connector for loose
connection. Check wiring between rear HO2S connector terminal No. 4
and ECM terminal A34 for an intermittent short circuit to ground. Also
check wiring between front HO2S connector terminal No. 3 and ECM
terminal A33, and wiring between rear HO2S connector terminal No. 3
and ECM terminal A19 for an intermittent short circuit to ground.
10) If fault is intermittent and signal is faulty, check
wiring between rear HO2S connector terminal No. 4 and ECM connector
terminal A34 for an intermittent short circuit of wire between


Code 5-2-1 (Front HO2S Preheating) Or Code 5-2-2 (Rear HO2S Preheating)
1) Check status message using Volvo Scan Tool (998-8686). If
PERMANENT FAULT, SIGNAL TOO HIGH is displayed, go to next step. If
PERMANENT FAULT, SIGNAL TOO LOW is displayed, go to step 3). If
INTERMITTENT FAULT, SIGNAL TOO HIGH is displayed, go to step 8). If
INTERMITTENT FAULT, SIGNAL TOO LOW is displayed, go to step 9).

2) If PERMANENT FAULT, SIGNAL TOO HIGH is displayed, turn
ignition off. Disconnect front HO2S Black connector and/or rear HO2S
Gray connector. Turn ignition on. Connect voltmeter between HO2S
connector terminal No. 2 and ground. If voltmeter reads about zero
volts, retest using new HO2S. If voltmeter does not read about zero
volts, check wiring between HO2S connector terminal No. 2 and ECM
terminal A14 (Code 5-2-1) or terminal A29 (Code 5-2-2) for signs of a
short circuit to voltage.

3) If PERMANENT FAULT, SIGNAL TOO LOW is displayed, turn
ignition off. Disconnect front HO2S Black connector and/or rear HO2S
Gray connector. Turn ignition on. Connect voltmeter between HO2S
connector terminal No. 1 and ground. If voltmeter reads battery
voltage, go to next step. If voltmeter does not read battery voltage,
check wiring between HO2S connector terminal No. 1 and main relay
connector terminal No. 3 for an open circuit.

4) Turn ignition on. Disconnect HO2S connector. Connect
voltmeter between HO2S connector terminal No. 2 and ground. If
voltmeter reads about zero volts, go to next step. If voltmeter does
not read about zero volts, check wiring between HO2S connector
terminal No. 2 and ECM terminal A14 (Code 5-2-1) or terminal A29 (Code
5-2-2) for a short circuit to voltage.

5) Turn ignition off. Wait about 2 minutes. Disconnect HO2S
connector. Disconnect ECM. Connect ohmmeter between HO2S connector
terminal No. 2 and ground. If ohmmeter reads infinite resistance, go
to next step. If ohmmeter does not read infinite resistance, check
wiring between HO2S connector terminal No. 2 and ECM terminal A14
(Code 5-2-1) or terminal A29 (Code 5-2-2) for a short circuit to
ground.

6) Turn ignition off. Disconnect HO2S and ECM connectors.
Connect Breakout Box (981-3190) to ECM connector. Check all grounds.
See COMPUTERIZED ENGINE CONTROLS in I - SYSTEM/COMPONENT TESTS
article. Connect an ohmmeter between HO2S connector terminal No. 2 and
breakout box pin No. 14 (Code 5-2-1) or pin No. 29 (Code 5-2-2). If
ohmmeter reads about zero ohms, go to next step. If ohmmeter does not
read about zero ohms, check wiring between HO2S connector terminal No.
2 and ECM terminal A14 (Code 5-2-1) or terminal A29 (Code 5-2-2) for
an open circuit.

7) Turn ignition off. Reconnect HO2S connector. Disconnect
ECM connector. Connect ohmmeter between breakout box pins No. 27 and
No. 14 (Code 5-2-1) or No. 29 (Code 5-2-2). If ohmmeter reads 1.5-13
ohms, code is caused by poor contact in ECM and/or HO2S connector. If
ohmmeter does not read 1.5-13 ohms, retest using new HO2S.

8) If INTERMITTENT FAULT, SIGNAL TOO HIGH is displayed, check
wiring between HO2S connector terminal No. 2 and ECM terminal A14
(Code 5-2-1) or terminal A29 (Code 5-2-2) for an intermittent short
circuit to voltage.

9) If INTERMITTENT FAULT, SIGNAL TOO LOW is displayed, check
wiring between HO2S connector terminal No. 1 and main relay connector
terminal No. 3 for an intermittent open circuit. Check wiring between
HO2S connector terminal No. 2 and ECM terminal A14 (Code 5-2-1) or
terminal A29 (Code 5-2-2) for an intermittent open circuit or short
circuit to ground. Also check HO2S and ECM connectors for loose
connection, contact resistance, and oxidation.


.....OK, where's my eye-drop.....


JPN

 

Holy descriptive. When I have a little bit more time, I'm going to read that whole thing, but just buy the length of it and use of larger words, I can already tell it's going to be good.

haha

 

I reset the code last night and have driven the car 3 times for a total of 40 miles. No CEL yet.

Last time I cleared the code, the CEL light did not come on for about 100 miles. Two days later. I guess I can hook up my code reader and try to read it real time.

 

Well, another day has passed and no code. It's been about 185 miles since I reset the light.

 

The CEL came back on about 2 hours after I left my last post. Turns out that I can reset the light and check it with the OBD-II code reader and a trouble code can be read almost immediately but it takes a day or so before the CEL comes back on.

I preformed a live reading and here is what I have:
Fuel System 1: Closed Loop, Fault
Fuel System 2: N/A
Load Value: 12.4%
Coolant Temp: 179 F
STFT - Bank 1: -4.6%
LTFT - Bank 1: -3.1%
Engine RPM: 2320 RPM
Vehicle Speed: 66 MPH
Ignition Advance: 27.0 deg
MAF Air Flow Rate: 3.0 lb/min
Throttle Position: 15.2%
Bank1 - Sensor 1: 02S Output 0.990V
Bank1 - Sensor 1: STFT 1.5%

Not sure what all that means but I know I have a fuel system closed loop fault.

I guess I will change my rear O2 sensor and see what happens from there.