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New PCM? (P1490 code)

 
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  #1 (permalink)  
Old 17 May 2017, 08:10 pm
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Default SOLVED!! New PCM? (P1490 code)

This issue is resolved! After all troubleshooting per manual, the PCM Relay power fuse (10 amp, slot 12 inside passenger compartment fuse box) was blown and would not allow the PCM to activate relays. Please read through this thread for details, and Thanks again to all who responded and helped along the way!

Hi folks, and thanks for all the help you have been so far. I need an educated opinion on my conclusion before I drop a few hundred additional bucks on a new to me 2001 PT Cruiser (Non-turbo 2.4) with 178,000 miles that is currently in "limp home mode".

The temperature sensor did not work when I got it, so I replaced it and the thermostat. I now get a temperature reading.

I received a P1490 error and tested the Radiator Cooling Assembly and found that the low speed side did not work. I have also never gotten the High speed side to work normally either, but it did test ok at the radiator plug. So,

1. I replaced the assembly, reset the code, and I still get the P1490 error, and the fan still doesn't power up as it should.
2. I tested the new fan at the radiator plug and the new fan tests good on both the low and high speed side.
3. So I checked continuity to every wire connecting to the fan (all 3), which is good.
4. I checked the relay on the low speed side. Applying 12v to the Radiator Fan Relay Control circuit (at the relay) and the relay clicks and the fan powers on.
5. So I remove relay and check continuity from PCM connector 2 pin 55 to Radiator Fan Relay Control circuit at the relay and it is good.
6. Reinsert relay and apply 12v to PCM connector 2 pin 55, and the relay clicks and the fan turns on. ( I also did this to pin 69 to test the high speed side and that works as well.)
7. Checked and cleaned the connectors to the PCM with electrical cleaner, pins all look good.
8. Put everything back together, clear the codes, and P1490 reappears and the fan does not work. (And I'm still in Limp Home Mode.)

Is it time for a new PCM? Does Limp home mode prevent the fan from working?

Thanks for your help!

Last edited by CRPerryJr; 18 May 2017 at 12:55 pm.
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Old 17 May 2017, 08:47 pm
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Default Re: New PCM? (P1490 code)

Welcome to the forum.

P1490 CHRYSLER - Low Speed Radiator Fan Control Relay Condition

Possible causes:
1. Faulty Radiator Fan Control Relay
2. Radiator Fan Control Relay harness is open or shorted
3. Radiator Fan Control Relay circuit poor electrical connection

I would suggest with the ignition off, pull the low speed radiator fan relay, start the engine and see if the high speed on the radiator fan comes on automatically. The P0490 will be triggered but you can reset that later.
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Old 17 May 2017, 08:57 pm
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Default Re: New PCM? (P1490 code)

Quote:
I would suggest with the ignition off, pull the low speed radiator fan relay, start the engine and see if the high speed on the radiator fan comes on automatically. The P0490 will be triggered but you can reset that later.
Thanks for your suggestion.
I just pulled the low relay, turned on the AC, and started the vehicle. No fan movement at all. Tried clearing P1490 code, but it keeps coming back. Still in limp home mode.

I used this procedure to test the fan.
P1490-LOW SPEED FAN CONTROL RELAY CIRCUIT
(It's for a sprinter, and in step 7, it wants you to ground instead of power the control circuit, but overall I think it's pretty accurate.)
And this schematic to help find the pins on the PCM.

Last edited by CRPerryJr; 17 May 2017 at 09:03 pm.
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Old 17 May 2017, 09:14 pm
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Default Re: New PCM? (P1490 code)

Quote:
Originally Posted by CRPerryJr View Post
Thanks for your suggestion.
I just pulled the low relay, turned on the AC, and started the vehicle. No fan movement at all. Tried clearing P1490 code, but it keeps coming back. Still in limp home mode.

I used this procedure to test the fan.
P1490-LOW SPEED FAN CONTROL RELAY CIRCUIT
(It's for a sprinter, and in step 7, it wants you to ground instead of power the control circuit, but overall I think it's pretty accurate.)
And this schematic to help find the pins on the PCM.
With the A/C off does the high speed fan come on?
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Old 17 May 2017, 09:28 pm
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Default Re: New PCM? (P1490 code)

Welcome to the forum

Try this reset procedure to see if it may get your PT out of limp mode:

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Old 17 May 2017, 10:15 pm
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Default Re: New PCM? (P1490 code)

Quote:
Try this reset procedure to see if it may get your PT out of limp mode:
Thanks for your suggestion.

I disconnected the battery terminals and connected them together, and opened a door and turned on the headlights. Nothing lit up. I left it that way for about 30 minutes, turned everything off, connected it back up, and the codes are still there. I did the key dance to verify the same code P1490, and started the vehicle with the AC on MAX. No fan movement. Verified that I am still in Limp Home mode as I cannot accelerate past 3500 RPM before the engine limiter kicks in. Verified one more time that the relay is working by applying 12v to the control leg of the low speed relay and it clicked and the fan spun.

One thing I did not mention before was that this vehicle sat without a battery for over 6 months.

I really appreciate everyone's suggestions, and look forward to more! I'm ready to try what ever it takes.
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Old 17 May 2017, 10:33 pm
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Default Re: New PCM? (P1490 code)

Quote:
With the A/C off does the high speed fan come on?
Hi and thanks for your question. Sorry I missed it earlier.

No, the High speed part of the fan does not come on with the AC off. even when letting the temp climb to a little less than 3/4 of the temp gauge. (My code reader gives live data and I allowed the temp to climb to 235 degrees Fahrenheit before shutting down the engine.) I had to wait quite a while and rev the motor to about 2000 rpm for a bit before she got that hot. But no radiator fan movement at all.
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Old 17 May 2017, 11:46 pm
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Default Re: New PCM? (P1490 code)

Are you using an OBDII Scan tool to get your engine trouble codes?
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Old 18 May 2017, 07:19 am
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Default Re: New PCM? (P1490 code)

Quote:
Are you using an OBDII Scan tool to get your engine trouble codes?
Thanks for your question.

I am using both a ODBII/CAN w/ABS scan tool (Innova 3160) and the key dance to acquire and clear the P1490 code.
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Old 18 May 2017, 08:31 am
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Default Re: New PCM? (P1490 code)

The inova should at least reset the DTC for at least a start and short idle before the ECU reactivates it for a issue. If it does not then you may a ECU issue

STOP using the key dance to try to resolve this issue you have,you will possibly cause other problems distracting from the first one.
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