GMC P2500 Manifold Absolute Pressure (MAP) Sensor Guide (1987-1989)
If your workhorse van is running rough, stalling, or getting poor gas mileage, the MAP sensor is a likely and easy-to-fix culprit.
- A bad MAP sensor is a common cause of rough idle, poor fuel economy, black exhaust smoke, and hesitation on these vans.
- Replacement is extremely easy, requires no special tools, and can be done in under 15 minutes.
- Look for OBD-I trouble codes 33 or 34, which point directly to a MAP sensor circuit failure.
- A new aftermarket sensor is a cost-effective and reliable solution for this repair.
Is Your P2500 Running Rough? It Could Be the MAP Sensor
A failing MAP sensor on your 1987-1989 GMC P2500 can cause a number of frustrating engine problems. Because this sensor directly tells the computer how much fuel to deliver, a bad signal can throw everything off. Recognizing the symptoms early can save you from poor performance, terrible gas mileage, and potential stalling.
Choosing the Right Aftermarket MAP Sensor
For a vehicle of this age, finding a brand-new original equipment (OEM) part from a dealer is highly unlikely. The good news is that aftermarket MAP sensors are readily available, affordable, and a reliable choice. Customer reviews for aftermarket sensors on similar GM trucks from this era are generally positive, with many noting that the new part fixed their running issues immediately. Since GM has updated this part's design over the years for better stability, a new aftermarket sensor will likely be based on a more modern and reliable design than your van's original part. Given the low cost, a new aftermarket sensor is a practical and effective solution compared to searching for a used part from a junkyard.
Cost of a New MAP Sensor (1987-1989 GMC P2500)
| Part Type | Price Range |
|---|---|
| New Aftermarket | $26.12 |
| New OEM | Not Available |
| Used OEM | $15 - $40 |
| Shop Labor | $50 - $100 |
Frequently Asked Questions
Where is the MAP sensor located on the 1987-1989 GMC P2500?
The MAP sensor is typically not mounted directly on the engine. On these models, it is usually found on a bracket near the air cleaner housing or on the firewall, connected to the intake manifold by a vacuum hose. Follow the vacuum line from the throttle body area to find it.
What are the OBD-I codes for a bad MAP sensor?
Your 1987-1989 P2500 uses an OBD-I system. The most common trouble codes for a faulty MAP sensor are Code 33 (signal voltage high, indicating low vacuum) and Code 34 (signal voltage low, indicating high vacuum). These codes will cause the 'Check Engine' light to come on.
Can I replace the MAP sensor myself?
Yes, this is a very easy DIY job. The sensor is easy to access and is typically held on a bracket by clips. The replacement involves unplugging one electrical connector, swapping a vacuum hose, and unclipping the old sensor to install the new one. No special tools are needed, and the job can be done in less than 15 minutes.
What's the difference between a MAP and a MAF sensor?
Your P2500 uses a MAP (Manifold Absolute Pressure) sensor, which measures engine vacuum. It does not have a MAF (Mass Airflow) sensor, which measures the volume of air entering the engine. Both sensors help the computer determine the correct air-fuel mixture, but they are different systems used on different vehicles.
Are there any recalls for the MAP sensor on this truck?
No. A search of the National Highway Traffic Safety Administration (NHTSA) database shows no recalls specifically for the MAP sensor on the 1987-1989 GMC P2500.
Technical Specifications
OEM Part Numbers: 12569240 16137039 16017460
This is a 1-Bar MAP sensor used for naturally aspirated engines. It connects via a 3-pin electrical connector and a single vacuum port.
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- GMC P2500: