Weird P1651 code today

Post by **Blacklab467** » 30 Nov 2021, 17:26

Took the wife and dogs out on a Christmas tree harvesting outing in the mountains today and my car got a "REDUCED ENGINE PERFORMANCE" on the highway coming home and went into limp mode. It happened at about 50 Mph on cruise control while I was using the accelerate mode on the steering wheel cruise controls. The car would then only go about 25Mph/ 2000Rmp approximately. I limped it like this for about 15 minutes to the next town where I had cellphone service and could call a tow truck if I had to. It idled rough and felt like it would stall but didn't. I decided to turn it off and then started it with no change. I then shut it off and plugged in my cheapo scanner and got the code P1651, cleared it out, and started it again and drove it home 50 miles without incident, it ran normal and the code didn't return.
My question is: what should I check so that this doesn't happen again? I don't have Vida and haven't yet researched the P1651 code on the forum. I'm confident to drive the car around town but don't want to take it to remote areas or the mountains till I am confident it is fixed. I have to go to New Jersey tomorrow for a week so won't be able to do anything till next Wednesday. Anyone have anything similar happen and can offer some advice? Thanks.

Post by **abscate** » 30 Nov 2021, 18:57

That’s a Volvo specific, computer system fault of some kind. It is not shown in my 2005 index

Post by **br0dy519** » 30 Nov 2021, 19:37

Taken from another post. I think I would start by cleaning the contacts on the ECM as a hail-mary.

P1651 ECM-981A Engine control module (ECM). Internal fault Intermittent fault

284: ECM-981A Engine control module (ECM). Internal fault. Intermittent fault, B5254T2

Diagnostic trouble code (DTC) information ECM-981A

Condition
Diagnostic trouble code (DTC) ECM-981A is stored if the engine control module (ECM) registers an internal fault which indicates that the normal engine control functions are producing a higher torque than is within the maximum permitted range. The diagnostic trouble code (DTC) is diagnosed at ignition on or with the engine running.

Substitute value
The engine speed (RPM) is restricted to approximately 2200 rpm by shutting off the fuel.
The requested torque is limited to a calculated operating range.
Possible source
Defective engine control module (ECM).

Fault symptom
Maximum engine speed (RPM) too low
Cruise control does not function at all
Uneven idle
Malfunction indicator lamp (MIL) lit.

Post by **Blacklab467** » 30 Nov 2021, 20:38

Thanks guys, at least I was able to clear it and things were normal. I'll probably keep driving it and see when it recurs. I really couldn't find anything specific on it either.

Post by **br0dy519** » 30 Nov 2021, 21:31

abscate, shouldnt blacklab have contributor status by now?? just saying....

Post by **abscate** » 01 Dec 2021, 01:16

br0dy519 wrote: ↑30 Nov 2021, 21:31 abscate, shouldnt blacklab have contributor status by now?? just saying....

Tough crowd, these Canadians ….

( I’ll ping Matt)

Post by **firstv70volvo** » 01 Dec 2021, 09:48

br0dy519 wrote: ↑30 Nov 2021, 19:37 Taken from another post. I think I would start by cleaning the contacts on the ECM as a hail-mary.

P1651 ECM-981A Engine control module (ECM). Internal fault Intermittent fault

284: ECM-981A Engine control module (ECM). Internal fault. Intermittent fault, B5254T2

Diagnostic trouble code (DTC) information ECM-981A

Condition
Diagnostic trouble code (DTC) ECM-981A is stored if the engine control module (ECM) registers an internal fault which indicates that the normal engine control functions are producing a higher torque than is within the maximum permitted range. The diagnostic trouble code (DTC) is diagnosed at ignition on or with the engine running.

Substitute value
The engine speed (RPM) is restricted to approximately 2200 rpm by shutting off the fuel.
The requested torque is limited to a calculated operating range.
Possible source
Defective engine control module (ECM).
...

If it is an ECM-981A code then it can also be due to other things than the ECM itself according to the link attached. MAF, throttle body position sensor, accelerator pedal. This dtc decode also mentions other codes should be generated, which is where VIDA would be a big help.

https://www.dtcdecode.com/Volvo/ECM-981A

jholden19 · Post by **jholden19** » 27 Mar 2023, 00:27

I got this code today driving on the highway with cruise control engaged in my XC90. The Reduced Engine Performance warning came on so I pulled over, shut down the engine and restarted it. This was the only code.

I am starting my investigation and only read the codes with a cheap scan tool. I will analyze with VIDA.

Blacklab467, did you get resolve this issue and if so, what was the cause?

Post by **Blacklab467** » 27 Mar 2023, 06:14

Interesting timing on this! My friend just had it on his 2005 XC90 2.5T last week. He said it came on while using "resume" on the cruise control on the highway, he said it was the third time this happened. Mine came on probably 3 times with the cruise on as well. I have never been able to find a cause or resolve this issue unfortunately.

jholden19 · Post by **jholden19** » 27 Mar 2023, 08:13

Thanks for your reply. It happened twice on the drive from Wyoming to NH and both times I was trying to resume with the cruise control. It had never happened before but I have noticed flakiness with the cruise control in the past where it would not hold the set speed and shut off. That was about a year ago and started working again without issue until this trip.

I should mention that I was driving with the rear half of the exhaust missing. The exhaust pipe broke between the cat and the resonator at the start of the trip. I struggle to think how that might come into play but figured it is worth mentioning. Perhaps the engine perceived insufficient exhaust back pressure?

I ordered the exhaust sections and will see if this issue comes back. I'll post updates on this thread.