1999-2009 [Subscribe to Daily Digest] |
Here's a SAAB bulletin on the P0420. #1 may not apply, but #2 might help
#1
Reference: Addressing customer complaints of MIL (Check Engine Lamp) illuminated and DTC of P0420 on MY00 and MY01 9-5 SE V6 models
When a customer presents a MY00 or MY01 9-5 SE V6 model with the complaint that the MIL (Check Engine lamp) is illuminated, and Tech 2 reveals only a DTC of P0420, the following procedure must be followed. If additional DTC's are present, they must be addressed first.
1. Check for abnormal running conditions. If poor running or misfires occur, those conditions must be corrected before any additional work/diagnosis is performed.
2. Check vehicle repair history for previous running problems. If previous misfires exist, the catalyst may have been damaged at that time. If so, the catalyst must be replaced, referencing the previous repair.
3.. If none of the above conditions are found, perform the following:
a) Drive the vehicle for at least 15 minutes to heat the catalytic converter to full operating temperature.
b) With the vehicle at an idle, connect Tech 2.
Select: Diagnosis / Engine / Trionic / Read Values
Graph: 02S1 and 02S2 signals
· Observe the two signals. While the 02S1 should oscillate constantly above/below .5v, 02S2 should remain steady at approx. .6v.
· If 02S2 does not remain steady and mirrors the 02S1 signal, the catalyst is not functioning and must be replaced.
· If 02S2 remains steady, the catalyst is operating correctly and should not require replacement. The DTC is most likely a "false fail" due to
a software problem.
4. Reprogram Trionic MY00 and MY01 V6 T7 ECM's using TIS edition 2002-2, SPS version 15 and Tech 2 version 43.000 to later to address P0420 complaint.
#2
Models:
1999 - 2006 Saab 9-5 All
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
CONDITION/CONCERN:
A technician may comment on a repeat P0420 set in the T7 ECM. The catalytic converter may have been replaced previously, and the DTC is often difficult to reproduce on a test drive. WIS diagnostics will lead the technician to replace the catalyst again if no other DTCs are setting.
RECOMMENDATION/INSTRUCTIONS:
If the above condition is encountered, the following information may help to isolate the root cause of a repeat P0420.
1. Diagnose and correct any other DTCs that are set prior to attempting to diagnose a P0420.
2. Perform the catalyst and IDM testing special functions with Tech2. T7 software should be updated to the latest release. If Tech2 determines a failed IDM or catalyst, repair as needed and re-evaluate the condition. Keep in mind that the catalyst test in Tech2 is capable of determining a restricted catalyst or inoperative catalyst, but it may not be able to determine a catalyst with reduced efficiency, causing a false "PASS" message. NOTE: MY 2004 Saab 9-5 with engine variant B235L (8th VIN digit "A") SHOULD NOT have the ECM software updated to the latest available release entitled "16 inch brakes replaced by 15 inch brakes" as this will cause a C0551 to set in the ESP system.
3. Diagnose and correct any misfiring or rich running conditions that are present, as these conditions will overheat and damage the catalytic converter.
4. Diagnose and correct any conditions which would cause the catalytic converter to become coated internally or chemically poisoned, thereby reducing it's efficiency. These conditions include coolant consumption, EXCESSIVE oil consumption, or poor quality/contaminated fuel. It is a good idea to have the tech share bulletin 04-06-04-047E (in Dealer World) with the customer, and verify the customer is using a "TOP TIER" fuel.
5. Check for any exhaust leaks upstream of the catalyst. This is especially important if any exhaust system components have been replaced previously, as even a very small leak between the pre-catalyst and post-catalyst O2 sensors will skew the post-catalyst O2 sensor voltage in relation to the pre-catalyst sensor voltage causing a false P0420 to set. A good way to check for leaks is to use a reversible shop vacuum to slightly pressurize the exhaust, then spray the exhaust from the catalytic converter forward with soapy water, watching for air bubbles.
6. Have the technician rebuild junction J16. Resistance build up in this junction can skew the O2 sensor voltages, and possibly cause a false P0420 to set.
7. A follow up test drive should be performed after any repair attempt per IRIS bulletin 248-9037 to verify the catalyst monitor has run. PIC4090
posted by 63.246.84...
, Sat, 17 Jan 2009 06:12:37
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